Im 9 weeks pp been having sex since about 4 weeks pp still haven't gotten period today i'm having what looks like mucus plug could i be pregnant?

Maybe: People who have sex tend to get pregnant. That's the way it's always been. Some women don't have a period for a couple of years, because they get pregnant before a first period after delivering a baby. To space children a year or more apart, people use contraception for a few months after delivery, or just avoid sex for a few months after delivery. Plan ahead, always.