Hello, I am an almost 19-year old female and my boyfriend and I have tried to have sex three or four times now, unsuccessfully. Each time he is hard and we use a condom, a few of the times he's gotten his penis almost in but it ends up slipping or it hurts me a lot so i shift positions, causing it to slip. I'm a virgin, I'm wondering how we can solve this so that we can finally have sex?