SMX-TMP DS and baseball bat

I was prescribed the drug for a bladder infection, and on the second day of medication I woke up feeling like someone had taken a baseball bat and beaten me with it. It was worse in my lower back (I'm assuming it was my kidneys that were actually sore), but my legs were sore too. Later that night after work I thought I'd do some light stretching of my legs thinking maybe it was just from being on my feet for eight hrs. About an hour later I was relaxing on the couch, and started experiencing a shooting pain on the outside of my left calf, 45 min later it dissipated then it happened again on the outside of my thigh, another 45 min go by it dissipates, then it comes back on my inner thigh, 45 min later, dissipates, and settles just below my knee above the calf on the inside of my leg. Soooo, I'm thinking I just stretched too hard or my legs were just that sore, but two days later I find bruises in the exact areas that the pains were.