I had an abortion and I stop bleeding the 2nd day. I had sex the fourth day now my period is back on is this normal my period is not all that heavy but it didn't happen till I had sex. They told me to wait three weeks but I had sex the fourth day whaht to

You . You will need to go see you doctor. The reason you are supposed to abstain from sex for 3 weeks is because your cervix is opened for the abortion procedure, and it takes some time to close and heal. You are at risk for an infection. Also, you are able to get pregnant immediately following an abortion, so protect yourself.