I also am on 500 mg azithromycin after being on the same abx IV for 3 months. I also experienced hot/cold, chills, sweating nervousness, weird feeling in my chest, etc. I believe you are just experiencing the effects of the new abx. I have started taking my oral every other day (on my own accord, not LLMD) as I read that this abx stays in your system for 66 hrs. Hang in there and hope (you will) you feel better soon.