Lyme can make some people loose weight,and others gain weight! It can also be from your thyroid or your adrenals not being right as well. Many people with Lyme also have Hashimoto's Thyroiditis, and also adrenal insufficiency, as Lyme can cause many auto-immune issues.
The best thing to do - since none of those tests are very sensitive until you are in severe need of treatment - is to read up on thyroid and adrenal issues, do some of the 'home tests' and then decide if you should pursue further testing.
Here is a great site that I like to use for basic adrenal and thyroid issues:
www.stopthethyroidmadness.com/ It has helped me to understand that I have issues with both my thyroid and adrenals.