I had an abortion last Saturday and took all the prescribed anti-biotics. I had some light spotting and a little bit of cramping for 2 days after, but then felt like I was normal again.

The following Saturday, I had sex. I know it was not the most responsible thing to do and would take it back if I could.

Later that day I started bleeding like a heavy period, and the cramping has started again.

Is this bleeding normal, and how long will it take to go away?

Go get it looked at the doctor... you could be hemorrhaging and that is a serious problem.