Boyfriend cheated early on in our relationship WWYD?

[headsawhirl]

Help need some impartial advice as I'm torn here.
I've just found out my boyfriend of a year cheated on me about 4 months into our relationship. He supposedly didn't sleep with her but he dated her and kissed her behind my back and openly lied to my face at the time. It was 3 dates then apparently he realised he loved me and called it off with her
At that point we had definitely agreed to be exclusive, at least a month before he began seeing her but we were taking things slow and hadn't said we loved each other or anything. We hadn't met friends or family but as far as I was concerned we were exclusively dating.
Since then we've become more serious, things have been great and he's recently met my children and is absolutely wonderful with them.
Our relationship has developed so much since that point but I feel like it's all been a lie now
I need to leave him don't I?

He should of thought about it before he keep doing it, no right to cry now because if you did it he wouldn't be forgiving you.
You probably can work through this and be happy again BUT you now know he can lie to your face and carry on a relationship with you with secrets.
What about when you go through hard times? Or you get pregnant and not so sexual active? Does he make another mistake he wants you to forgive?
This is hugely unfair to you and what ever excuse it's just that and excuse for being selfish.

His justification is that at the time he wasn't sure how I felt about him and didn't think that we'd get as far as we have

Agree, that's crap, and making it your fault.

He's trying to get off on semantics. It doesn't matter if you were exclusive- the only important bit is that he lied, repeatedly.

You're in for more of the same if you stay.

This happened to me - early start of relationship but he was also seeing someone else. I found out when she facebooked me to tell me. I gave him a second chance after much pleading but it didn't work out. He was 2 hrs late coming to mine for a night out - I couldnt reach him - his phone was off and then I knew I couldnt trust him. Also a few other red flags like lovebombing and I know he had shown me who he really was early on. Time to end it.