Someone please help me!

I'm really worried. So Friday, my period ended and I went back to school. For the last year I've been out of school due to personal reasons, and it was my first day back.
I had a cold that week and my doctor gave me antibiotics to help. It was something with my sinuses I think.
When I got home Friday I had diarrhea. I pooped twice (this gets TMI from here on out) and I was scared to even fart because I was worried I'd poop myself. It's Saturday night and I'm still on the toilet and still pooping. I'm worried something might be wrong with me. Please help me ASAP!