I found out I didn't have to wait to get blood test even I am on antibiotic right now per my doctor.
You should talk to your doctor, to be sure; however, I've had thyroid blood tests done while on antibiotics and it's never changed the results.
Is TSH the only test you are getting done? You really need to have Free T3 and Free T4 tests done, as well. TSH is a pituitary hormone and is not always indicative of actual thyroid status.
Have you already been diagnosed with a thyroid condition? Are you currently on thyroid medication?