Unfortunately, you sound like one of the many treatment failures of the standard 3 weeks of Doxy. It's going to be harder to kill at this point, so I also ditto Jackie's suggestion to find a LLMD asap before it gets even more established in your body.
Welcome to MedHelp Lyme.
There is a split in the medical community about whether a few weeks of antibiotics (abx) is enough to eradicate the bacteria. Many docs say it is, but there is a substantial minority opinion that Lyme is a much more complex disease than run-of-the-mill infections and requires much longer treatment, because the Lyme bacteria have particular characteristics that allow them to evade a short course of abx: the Lyme bacteria have a very slow reproductive cycle, and antibiotics are effective mostly when the bacteria are dividing, therefore a longer course of treatment is called for, as is done in tuberculosis (usual treatment time: 18 months). Also, Lyme ticks have a means to create slimy shields ('biofilms') in the body that keep the immune system from locating and killing the Lyme bacteria. In addition, perhaps half the ticks that carry Lyme also carry other diseases that must be tested for and treated separately from Lyme.
It sounds like your doc is in the traditional group and gave you the standard treatment for an earache, not for Lyme. My suggestion would be to find a Lyme specialist for a second opinion. It can be tricky finding one of these docs who thinks bigger thoughts about Lyme, because they are looked down on and sometimes threatened with loss of their licenses for treating longer than a few weeks.
You don't have to buy in to the concept of longer treatment if you do see a Lyme specialist, but I would urge you to see the doc and hear him/her out and then decide, because if you do have Lyme and any co-infections, the sooner you are treated, the better. There are some quackish docs who play in the Lyme field, just like in any group of 'professionals', so you also have to keep your eyes open, but not all Lyme docs are quacks, never mind what mainstream medicine says.
We patients sometimes call the broadminded docs LLMDs, slang for Lyme Literate MDs, meaning they think the bigger thoughts than two weeks of abx and you're done. An LLMD can be any kind of doc, and they are seldom infectious disease docs, who as a group deny that Lyme is persistent. (Note that the 'Lyme deniers' have a theory that if you still have symptoms [as you do now] after treatment, it is not because you are still infected, but because your immune system is overreacting to the now-eradicated infection. They call this 'post-Lyme syndrome.' Not very logical imo.)
Finding an LLMD can be tricky because they are not popular with the mainstream docs, and in some jurisdictions have been hauled up before medical boards for treating too long w antibiotics. Thus they often stay underground, depending on the state in which they practice.
If you tell us which city/state/area you live in or can easily get to, we may be able to give you some ideas on how to locate an LLMD for a consultation......
It's what I would do, and indeed what I did, but it took me shopping through 20 docs to finally be properly diagnosed since I didn't know any of this then!
Best wishes --