Deciphering: I’m Not Looking For A Relationship

I've encountered the phrase "I'm not looking for a relationship right now" many times from men, and like many women, proceeded to hop in bed with the guy anyways. The results of having sex is as you would expect: they still don't want to date you even after you put months of time hanging out and sleeping together!

How do I tell her I just want sex?

I just met a woman who I knew I wasn't going to date based on her personality, and we slept together. I didn't feel super bad about it because she just got divorced and seemed to be enjoying her freedom. We've been continuing as it started, just sleeping together and having fun.

Losing Interest in Lovers

I have a pattern of dating around a lot and seem to constantly find myself hooking up with people I'm not all that interested in. At first, they intrigue me, but my curiosities about them don't last for long. Usually, I'll end up sleeping with them, then realize that I'm not interested in them.
I've wondered whether one way of resolving this is by being clear with people that I may only want sex. The trouble is that I'm not always sure that I'm only after the sex, since I'm also looking for connection.