Painful beginning of penetration

Two months ago I finally lost my virginity after a few tries and thought it would fix my problem with painful beginning of penetration. But still, whenever my partner tries to enter it hurts (a lot after short foreplay, but after long fingering session it's still painful). What could be the cause? Or maybe it's normal? I want to fix this because I love sex with penetration, once he's inside everything feels great and I can slide it out fully and take back inside without the pain...