I don't, and I seriously doubt the claims from others that they can. There just aren't any nerve endings that deep in the rectum to feel an ejaculation. That's not to say that one is unaware that the man is reaching his climax. From his breathing rate, the way his body stiffens, the way his penis throbs inside you and other body language (and sometimes oral exclamations), you know he's gone over the top.

And this can be an extremely rewarding feeling. Even if your body is not built in such a way that you derive a lot of physical pleasure, the emotional and psychological pleasures can be enormous. If the guy is really hot and/or if you are really fond of him, the knowledge that he is using your body for his sexual pleasure is very fulfilling.

From your questions I gather that your butt is virgin territory, but you are interested in giving away your virginity. Please be careful. MAKE ABSOLUTELY CERTAIN THAT THE MAN WEARS A CONDOM. If you wish, you may send me a Private Message if you want more personal information.