I'm sorry it's taking so long for things to get sorted out for you, and good for you for *not* giving up!
From what I read, it's not unusual for symptoms of Lyme etc. to come and go, and to be quite different in each person. That's part of what confuses docs who aren't tuned in to Lyme and its co-infections. When the 'Lyme' tick gives someone Lyme disease, from what I read, there is a good chance (maybe 50/50 chance?) that the bugbite can also give you another completely different infection at the same time: for example, I had Lyme and also had babesiosis.
The tests for Lyme and 'babs' are completely different from each other, which is why an expert in Lyme disease generally also need to be an expert in the other infections the same tick can carry. Docs who aren't experts in that way can easily miss subtle symptoms and can also miss later clues that something other than 'just' Lyme is at play. No testing means no diagnosis and treatment. Also, there are different tests for Lyme, and MDs who use the less accurate tests often miss the diagnosis.
From what I read, it is not unusual for symptoms of Lyme and possibly other co-infections can rise and fall over time. If you don't have copies of your previous tests, your earlier MD can give you copies of them, and that may be helpful to a new doc to see what's up. That's what I would do ... and it's important to have an MD who is an expert in Lyme, tho they *all* think they are experts, which makes it a little dodgy to know if you've found one who's really on top of things.
If there are groups for Lyme patients in your area, you may find good recommendations for a Lyme doc with a different point of view from the previous one. If you have copies of your old tests, take copies to the new doc, because it may be very useful to a doc who knows how to 'read' Lyme etc. As a culture, we are accustomed to docs knowing everything there is to know about various illnesses, but when a new one -- like Lyme -- comes along, the docs often are not up to speed for a while ... and for years. If you don't have copies of your old tests and don't want to call up the old doc, that's okay ... the important part is a fresh look by a new doc. I'm not medically trained, but as a patient, that's what I would do.
Since all MDs think they are entirely correct about everything they work on (or they wouldn't be practicing medicine!) finding a good doc is the trick ... If you can't find a new Lyme doc nearby, then go to the ILADS website and ask for names of MDs near your town/city. Also look online for patient-oriented Lyme groups in your area or even your state: there are often good networks among 'Lymies'.
Let us know how you do, okay? Best wishes!
... and PS:
Be sure to ask the doc's office for ALL pages of ALL tests, not just the summary pages and not just for the most recent tests. To save copy paper, toner, time, and aching feet standing at the copy machine, docs' offices sometimes (too often) will copy only the most recent test or only the summary page without the details.
Specify to the doc's office that you want ALL the pages in your file, and do it in writing so they can't say they didn't know what you requested.
The more data you have, the more information your new doc can look back on to see the big picture.