I sometime get lowers stomach pain after having intercorse with my boyfriend?? what does this mean?? i'm a chubby girl but not fat

Possibilities: If your boyfriend's penis is hitting your cervix on deep penetration, that can cause pelvic pain. That's my first guess based on the information you gave. You may also want to try a different position to see if it helps. If it is a persistent problem, see your doctor to make sure there isn't an infection or other problem.