I need some advice!

This has been happening to me quite a bit lately and I need to know what i'm doing wrong.

So I have been lurking on TRP for quite some time now and my game has definitely improved.

getting girls has never really been an issue for me. The real problem comes when I bring them back to my house. For some reason, I cant gain any closure. I mean, everything is always going great, we kiss, have fun, mess around, but when it comes time to have sex, it doesn't happen. They always run away right when it's time to get serious.

why is this happening to me?