I was prescribed Sulfameth/Trimethoprim 800/160 Tabs for a bite ...

I was prescribed Sulfameth/Trimethoprim 800/160 Tabs for a bite on my leg from unknown origin (spider, tick, scorpion...nobody seems to know, and neither do I) and I had to take it for 10 days, twice a day. and I just felt horrible for all 10 of them. nausea, headache, intense back pain, no appetite (just thinking about eating would make me feel sick), and I also had really bad dry mouth. The 10 days ended 3 days ago, and I'm still feeling these side effects, although my appetite is slowly coming back. But this morning when I woke up, my whole body was burning hot and I had a bright red rash on my face that was very hot. The rash has been there all day, and it's really painful. All of this, and the bite on my leg is actually WORSE than when I went to the doctor to get help for it!!!