Who kisses better?

Seriously. A person can fake a lot of things, but can't fake a good kiss. It takes real feeling and exquisite attention.

Mr. Once-A-Week kind of sounds like he's working on the "friendship with benefits" model. His comment that "we are what we are" and lack of concern over you dating Mr. Sweet make me think that. Whereas you might be working off a different model, in fact your model is so different that the whole situation with Mr. Once-A-Week has you making yourself sick and staying up all night.

Add to all this the idea that Mr. Once-A-Week is so inadequate to your needs that you were capable of having a serious interest in someone else in the first place.

Your instincts know the answer.