Pain & Being Swollen

Me and my boyfriend are in a long distance relationship so every time I see him, we have sex. On the first night of visiting him we usually have sex and the next day we try to go at it again but I get (for lack of better term) swollen “down there” and he can’t put it in bc it hurts too much. A day later, we’ll have sex and I’m completely fine but I hate having to wait a full day to have sex with him because I’m trying to get back to normal instead of my vagina being “swollen”. When I say swollen i mean my vagina gets really really tight and I don’t know what this could possibly be? Is it because of his size? Is something wrong with me?