Hi. Well, I think we are asking the wrong questions here. Your guy cheated on you. That is where your focus needs to lay. She may or may not be pregnant by him but the reality is . . . she could be. There is a chance because he had sex with her.
This is not a man you want in your life. This is not a man you want to have a child with. This is not someone you want to be stuck with for the rest of your life because you have a child together.
So, I think you break up and move on completely. I'd wait until someone cares enough to ask you to marry them and by doing so says publicly that they are committed to you before you even talk about having kids together.
That is my best advice to you at this point. You can do better. good luck
"me and this guy" - "this "GUY"?????
You asked what should You do
YOU SHOULD STOP TRYING TO BRING (another?) BABY INTO THIS MESS !!!!!
So, you're trying to get pregnant by a guy, who may have just gotten his ex fiancée pregnant?
What doesn't "add up" is the fact that you're still with him!