Not all parasites can be eradicated with antibiotics...you may need medication that deals specifically with the parasite(s) you may have... Example is malarial parasites require anti-malarial meds, giardia requires Flagyl/related meds, etc.
Genova is a lab that has a good reputation for more accurate parasite testing - might be good to ask your doctor about getting tested through this lab. Might take a couple of tries to detect the parasites, also.
Another thing is that Lyme is entirely capable of hiding deep in tissues, biding its time before it comes out of hiding and starts causing problems (it is closely related to Syphilis, which has been known to do this). It is possible you picked up some other infection on your trip 2 years ago, which then weakened or side-tracked your immune system enough to enable the Lyme to come out of hiding and thus be detected on the test.
If you have had Lyme dormant for so long, it is possible you may not find help from antibiotics until you've been on them for a longer time. Also, if another parasitic/other infection that doesn't respond to antibiotics (such as certain parasites, fungal or viral infections) is dominating right now, this may be overshadowing the effects of the antibiotics such that you don't feel any better...
It is also thought by some MD's that sometimes other infections (viruses, other bacteria) can cause cross-reactions with some of the Lyme Western Blot test bands and result in a positive result on those bands when you may or may not actually have Lyme. I don't know that I fully agree with this, but since it is reported in various research articles, I'm bringing it up here.
Also, if there is some environmental exposure (toxic mold, chemical outgassing, water contamination, etc.) you are getting more of since retirement, this may also be something you need to consider looking in to as a possible cause or contributing factor to your symptoms. One way to test this is to go on a trip somewhere for a week or so and see if you feel different/better during that week than when you are at home.
You might also consider consulting a Naturopathic physician about your symptoms and see what their take is on all of this.
I hope this gives you some ideas of things to discuss with your doctors.
Chronic Lyme Disease, Bartonella (clinical dx only), Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD ("Secondary Lupus-Like Syndrome"), Osteoporosis, etc.; G-Tube; TPN via PICC (trying again to wean off the TPN).
Meds: IV Cipro, Heparin (to flush PICC line), Singulair, Claritin, Domperidone, Colloidal Silver, probiotics, digestive enzymes, Milk Thistle & other liver support herbs, Magnesium, homeopathy.