After inter coarse, i started feeling pain in my uterus. ?

A few ideas: Pain in the uterus often means infection, thus it might be wise to see a doctor to get checked for stds... Something 19 year olds have to be on the lookout for. It could also be around the time of your period and the pain is pre-period pain? Regardless, unless you use a condom every time you have intercourse, it's best to get checked for stds, as they can cause infertility if left untreated.