Well I am so sorry that you are going through this without insurance I know that must make things sooo much harder! Your body will change from 12 to 25 drastically, so i wouldn't count on it being just tendonitous. Do you qualify for assistance through Medicaid? (you would be surprised at who qualifies..) Anyhow, the lime disease would be contracted through being bitten by a tick...so unless you've been camping.... or live in the woods i wouldn't count on that being correct! Now the RA will typically have very distinct SYMMETRICAL features * meaning if it is on one side it will be on the other! For instance both of my hands, both feet, both shoulders, on and on have been affected by the RA. unfortunately, there is not one single test that can tell you if that is what you have... however, there is one single DOCTOR that can...you need to see a Rheumatologist to get a proper diagnosis. Now if they feel that this will need further testing they will send you to a Neurologist (for example) if they think it could be a nerve related issue. Typically with RA it does not cause numbness, but other similar autoimmune diseases DO, such as MS. I would definitely get this checked out and keep going to the Dr until they are able to give you answers, you must take good notes and be your own advocate! I found that it is much easier to try to ignore it but far more detrimental to your health.
Honestly the only reason i continued going to the Dr. was because i promised a friend of mine that I would until they figured it out. Now since that promise was made my friend has passed away at the age of 30. She died from cancer that the Dr.s had missed, she knew something was still wrong and waited a year to get it checked out again...by that time her cancer was already at a Stage 4. She fought very hard but did not win her battle. The moral of that story is had she trusted her gut and gone to a different doctor when she knew something was still wrong, maybe she would be alive today. Please please get it checked out and let me know how it turns out.