Sooo, i've been dating my boyfriend for a little over a year now. The issue i am having is whenever we have sex everything is great and dandy the first round, but then once we finish up my vagina becomes swollen[including the flaps and clit] but only slightly swollen, and hurts pretty bad the rest of the night. this happens a lot and usually after we have sex. but the strange thing is this didn't happen when we first began having sex it happened like a few months in. i'm just curious as to why this may be happening as well as what i can do from preventing this from happening because after awhile it begins to hurt and i can't really continue any longer. 

a few facts, i am a rather small girl...only a little over 5 foot and he is a pretty large um, man. soo idk if this may play a part...although this wasn't really happening until a good 3 or 4 month in. also, we do have some somewhat rough sex now and then but not all the time, and even on the times we have simple sex it does it?

Can anyone help?