I am a 42 y/o woman rxed sulfameth far a UTI. I just completed my...

I am a 42 y/o woman rxed sulfameth far a UTI. I just completed my 5 day rx. From day one I had diarrhea, and stomach upset, but for the past 2 days I have heartburn which was rivaled only by the hearburn when at the end of my pregnancy with twins. It burns when I eat, and when I don't. I have gas, and the burps. And today I have begun to have joint pain in my jaw, throat, and in my chest if I take a deep breath. The strange thing is I have taken Bactrim in the past with no ill effects. Is the generic really that different...or am I just old! Hopefully the side effects will subside now that I have completed my course of meds. (it also made my chronic eczema worse...but just about anything can trigger that)