I'm a single mom. I was "with" my ex until I was about 7 months pregnant or so...And then we broke up and now my daughter is 3 and a half months old. He's never seen her, and I wouldn't change that for the world (unless of course he was a decent person). When we were "together" he never helped out or was any kind of support system, so I still feel like I did the whole pregnancy on my own. All he did was cause more problems then he was worth. I wish we had broken up sooner, to be honest, I think I would have been so much happier and been able to enjoy my pregnancy to the fullest.
If he is missing out that is his fault. Don't feel bad, your baby will have as much love as it needs through you and your family/friends.
Atleast with me, I would much rather be single and alone for the rest of my life then be with someone and not be truly happy. I think your baby would be a lot more unhappy too if it was raised in an unhappy household full of cheating and lies. Children are very perceptive, and he/she would pick up the tension and unhappyness right from birth (even while it's still in the womb it can sence your feelings and react to it!).