What Causes Burning Sensation In The Vagina After Intercourse?

My husband & I have been married for 2 months ~ we waited to have sex until we were married & after the first week or 2 all of a sudden, it started burning for me. It's a burning sensation on the inside and it's not immediately when he enters but soon after it gradually starts to burn and then it seems to get worse after we're done. It lasts for about 10 to 20 minutes after. I can urinate just fine afterwards and we've tried extra lube. Is it just that I'm still not used to it? (He's in the military and we just spent a month apart) He is rather large, is this something that will go away the more we do it? Could it be that he goes too fast or is this something I'm just going to have to live with?