Please help me answer a med. question relation to constant UTI's?!?!?

I am trying to figure out a correlation between both antibiotics and why they make me so ill. One is a sulfa so I looked up macrobid, and it is not (so that's not my answer). I am going to the doctors soon but as we all know, they don't always know everything.... I get extreme nausea (dry heaves) tenderness to upper gastric area, and dizzy, lightheaded, and pale. I just don't see how I could be "allergic" if I felt the same way while on bactrim. I am eating before I take it too?!?! So confused. Not asking for rude criticism, just someone who could maybe relate or has an idea to look further into. Thanks so much!