Zithromax Z-Pak and weight watchers

While I have taken it before, I don't recall having anything but very mild side effects (maybe a little discomfort in my belly). This time, however, it is different and I am owing it to the beauty of aging. I just took the second of the three pills (and yes, I've had the three pill one before). My bronchitis is clearing but this afternoon I had really bad abdominal pain and I have a continuous headache in the back of my head, where my spinal cord ends. It is not as bad (so far) as the one I had with Biaxin (I refuse to take that). The only bright side is that it made it a really good time to join Weight Watchers because I do not have much appetite. I was able to sleep last night, at least, because my cough decreased. The verdict is still out on whether I would do this again. Problem is, I am allergic to Penicillin.