HI D. Both Lyme and thyroid disorders can cause a low body temperature.
Which thyroid tests did you have done? It is important to have the Free T3, Free T4 (besides the T3 and T4) and thyroid antibodies tested in addition to the normal panel. They are not usually done but are necessary for a comprehensive view. If antibodies are present, other results may be normal but treatment is warranted. Even if your results are in the normal range, they may not be normal for you. Some people have Lyme and a thyroid disorder.
Lyme disease can affect thyroid, adrenal, and hormone function. I believe anyone who has Lyme should have this testing done.