Welcome to MedHelp Lyme --
You are wise to try to sort out your medical situation -- some infections (including some you mention above) never go away by themselves, and appropriate treatment is needed, such as with certain antibiotics for a particular length of time.
You say, "I doubt that I have lyme disease since I live in Las Vegas and it seems uncommon." Even uncommon infections afflict some of us, and Lyme is one of those. For a long time now, much of the medical profession has taken the position that Lyme is rare, hard to get, and easy to cure, which leaves out the fact that some diseases that start out looking like 'rare, hard to get and easy to cure' will then spread through the population, making more people sick over time. While we don't see much of that kind of new and spreading disease, there are always some, because Mother Nature is always cooking up new tricks.
Bottom line: don't assume you couldn't have a disease because it is rare. All diseases that are now wide-spread started out as uncommon (one example: AIDS). Whether you have Lyme, or bartonella, or some other infection from your pet or a walk in the woods or another human or some other source, I would find a knowledgeable MD for a work up to determine what tests you should have, to rule out (and rule in) whatever ailment you have, and then to consider what treatment is called for.
You mention Lyme and bartonella and allergies, and that is what a good doc will help you sort out: what your symptoms are, how long ago they started, and so on. Then when tests of the possibilities are run, you're at the next step of figuring out what you have, and then the last step will be how to treat it. The important thing is not to assume that Ailment A cannot possibly be the problem just because it doesn't seem likely. It's the medical exam and history and tests that are done that will give the doc the data to know what you have.
The most important part of all this is to locate and work with a wise MD who doesn't assume what you have or don't have, but instead works on the basis of evidence. And here's one more issue: there is much confusion in the medical world about Lyme disease, and many MDs believe strongly that Lyme is not a serious infection and can be cured with a few weeks of a common antibiotic. That is how the earliest MDs to study Lyme viewed things just a few years ago, and those MDs have had a strong hand in labeling Lyme as an infection that is rare and easy to cure.
Many of those MDs who worked early on the newly discovered 'Lyme disease' believed that it was rare, hard to get, and easy to cure with a few weeks of a common antibiotic, doxycycline. It was a good first step in the investigation of how to diagnose and treat Lyme ... but most of mainstream medicine simply stopped thinking at that point and assume that all the aspects of Lyme were now known. Full stop, and no further investigation.
Those MDs are still around and still believe in their early assessment that Lyme is (all together now:) rare, hard to get, and easy to cure. Those MDs also have too often closed their minds to the possibility that NOT all is already known about Lyme. That is why it is very important to find an MD who thinks broader thoughts about whether you have Lyme that has not been diagnosed and/or cured.
I personally went through 20 trained and experienced MDs who could not figure out what I had. Doc #20 finally ran a test for Lyme disease (since everything else had been ruled out), and the test came back positive for Lyme! But then Doc #20 said, "You cannot possibly have Lyme. I have patients with Lyme, and they are all near death." Really? Then why not consider that maybe the medical profession was overlooking something serious here??
I'm not medicallly trained, but knew from an old friend who had Lyme that it is indeed serious and needs an MD who does more than shrug, so I took the positive test results from Doc #20 and found a Lyme specialist. How do you know that a doc who says s/he is a Lyme specialist really does understand more about Lyme than most docs do? One way is to look for an MD who is a member of a voluntary medical association called ILADS (pronounced EYE-lads), which is short for International Lyme and Associated Diseases Society. As in all professions, not all ILADS docs are as good as others, but ILADS is a good place to start, as are Lyme patient groups you may find in your area, who can guide you to good Lyme doctors nearby. Treatment for Lyme and any co-infections you may have often extend to months. I was in treatment for about 9 months total, for Lyme and for one co-infection, called babesiosis, which is often carried by the 'Lyme' ticks.
You give a good description of your symptoms so far, such as brain fog. Also, bartonella is a common co-infection carried by the 'Lyme' ticks, so it's quite possible to have Lyme *and* bartonella at the same time. These infections require different testing and different treatment from each other, and there are perhaps a half dozen other infections that also may come along from the 'Lyme' ticks (such as my infection with Lyme and babesiosis). A good Lyme doc will know all about these things.
I wouldn't worry about when you got whatever infections you now have. I would instead find a wise MD who understands Lyme disease (such as an ILADS member doc) and go in for a review of your history and symptoms and any treatments to date, and let the new doc piece it all together to give you a diagnosis. If you don't like the diagnosis, then see another doc ... but don't quit until you have answers that make sense based on science and not on old assumptions about Lyme that are still held by many MDs.
You say, "I read a lot of bartonella patients also complaining about brain fog. Perhaps ... the symptoms never cleared up because [a pet] continued to bite and claw me on a regular basis for years." Maybe. But maybe it's just that you have already been infected for all those years.
I know you are working hard to figure out what you have been going through, but I would (if I were you) find an ILADS-member MD for a work up and see what data and test results you get back.
Lyme isn't a do-it-yourself thing, and finding a good ILADS-type MD is what I would do. It's definitely worth it, because Lyme and its co-infection don't go away by themselves.
Best wishes -- and good health ahead! Keep us posted, okay?
Given the rapid spread of Lyme in the past few decades, I would guess that Lyme is pretty much everywhere and not focused on cold and wet areas. It amazes me when the medical profession sets firms boundaries of where certain diseases supposedly do and do not live, because the ticks don't need anyone's permission to move along.
Sorry to hear you are not fully recovered. I hope your MD is a good one. You might consider a second opinion. The medical profession is still catching up with Lyme, as they tend to do with new ailments. I went through 20 MDs to get a proper diagnosis, and Doc #20 was the one to get me fully well again. Best wishes --