Hmmm... it's possible this guy is cheating on you with your ex, but if I had to lay bets I'd say the ex is making all this up, and she's a jealous b1tch who hates seeing her ex- being happy with someone new and wants to split you up because she is under some deluded belief that they can get back together. Or maybe she doesn't want back together, but just can't stand to see him with someone else. I could be wrong, but that's my guess.
People lie for all sorts of reasons, not just cheating. I don't know the circumstances, or what he lied about, but it's entirely plausible that he lied just because he didn't want to get you upset or angry, given how you already feel about his ex. I don't think it was right that he lied to you, but he could have genuinely been trying to protect you. You need to let him know that you'd prefer to hear the truth, always, even if it upsets you, than have him lie to you to protect you. In the long run the lies hurt more, as you've found out.
You have a kid with this guy, so I wouldn't rush to leave unless you were a lot more sure that he was cheating, and even then not until you'd had a go at patching the relationship up.
Sounds like a
big fat mess to be in, also his ex and the child will always be in his life, so if you cant live with it , now is the time to leave before it gets worse luck jo
Well, they DO have a daughter together, so they must stay in contact with each other. His ex could be lying, telling you things just to get you to break it off with him, so that she can have him back. That is a possibility. If you don't trust him, then you need to break it off. Period, end of story.