Bactrim Erge, Urine Test, Chest Pain, Uti, Antibiotic

well i had a UTI before and i went back to the doctor's like a couple of weeks later because i felt the erge to pee like every 3 mins. i had to take a urine test and a doctor (not my doctor) prescribed bactrim because she suspected that the UTI i had before never finished. after 2 days of taking it i was all stressed out then all of a sudden i couldn't breathe and my chest was in BAD pain so i went to the emergency and they said nothing was wrong. the next day (Thursday) i went to school (that week i only went to school on Monday) and i had that same chest pain, i went to the nurse and my mom came and we went to the hospital. they changed the antibiotic to Cipro, but the thing is, is that i worry a lot over the antibiotics that im taking and i just dont know what to do. i do have pains but not that much in the chest, it's like it travels all over my body. I DON'T KNOW WHAT TO DO! PLEASE REPLY BACK!!!!!