My love, your issue here was with finding out the first time. When was that? couple of months in? 6 months tops? had you have set the boundary line THEN, you would not be in the position of thinking you are in love and having the thoughts about your DD etc
The fact is that he's cheated on you all the way. The BEST message you have for your DD is to show her that you are worth more than this and that she should never settle for a liar.
I know you struggle with relationships, (been there, done that) but until you set your bar higher, you will keep repeating this cycle. Had your bar been higher, the 3 'failed relationships' would probably should never have even got off the ground in the first place and you would have been available for healthier relationships.
Sometimes we have to do what we need to do, even though it's hard and its not what we WANT to do. Its this time now for you. You are worth more than him, way more!
End it asap, get him out of your life and when your DD is old enough to know, you can tell her that you wanted to be in a relationship with only him, but he was lying to you and had other girlfriends, which isnt acceptable to you.
please be kind to yourself, its the first step to loving the person you are and it helps you set your bar higher so you won't have this kind of chancer in your life again.
Demand better! you're worth it and then some! (((hug)))