I'm so tired of these infections!!

Hey guys, so I'm in a long distance relationship and I get to see my fiancé about every two months for about a week or two I stay with him, so as you can imagine when I see him we have A LOT of sex lol, but EVERYTIME I visit him I get a UTI. And yes I've read up on it, I've tried everything, I know the drill believe me. Cranberry juice didn't work (was drinking it everyday) used the bathroom before and after sex, that didn't work, I chugged lots of water everyday. I really don't know what else to do. I've tried all of the recommendations, nothing's worked. I only get these when we have sex. The only thing I can think of is to make the sex less rough? Maybe he's too big for me? Is there any medication or something that I can get on so I won't get this every time we have sex?