I'd agree with BeachGierl as well. The symptoms can be rather from antibiotic treatment, than from Activia, but.. Have you taken Activia before? I mean, before the sinus infection and antibiotics. If so, and everything was ok, the the meds for sinus infection are in the spot. On the other hand, Activia could add a thing or two, as it has some not too great ingredients. If you started it after infection, and not eating it before - I'd try some other probiotic , maybe even just a pills, to avoid the diary products for a while. I'm not lactose intolerant, but most of the diary products makes my gut to over work
So, I've never even tried Activia