What Causes Pain In My Vagina After Intercourse?

Hi, When im pregnant i got my hiv test done in 3 months(which is negative), but during 5 month i often got severe pain during intercourse and after intercourse. And after delivery also i had same problem. Gyn. suggested oflamed-oz tablet, now there is no pain during intercourse but after intercourse there will be some pain...can u plz tell me what is actual problem?