Any other mommas have this happen?

About a month ago I was getting cramps and went to emerg to get it checked 2 weeks ago. They couldn't see the baby in the ultrasound and said it could be the start of a miscarriage but they heard the heart beat so they took some blood. They got the blood work back yesterday and said that the babies okays and I'm 8-9 weeks pregnant but today I few hours after having intercourse I started lightly bleeding. I don't know what's going on.. should I be worried?? Has any other mommas had this or something similar happen?