Break up with S. He's an unattractive mess. Tell him that you wish him very well, but that he doesn't seem to be in a place in his life right now where he can handle the kind of relationship you have, and that you'd like to end it.
Don't tell him you're pregnant. He can find out with everyone else at 14 weeks or whatever.
And, yay, more pregnant people! We've had a lot on the board lately (I'm pregnant too--34 weeks!). Congrats!