To be honest mate and this is just advice, leave! Don’t be with someone who doesn’t respect you. Once a cheat always a cheat. You let this go she will think she can do it again and again and you will forgive. Plus you won’t really ever forgive her and it will cause issues in the relationship in the future.

Ok as for the pregnancy. Be around but at a distance and get a DNA test done as soon as possible to determine if your the father or not.

If you are the father than be there for your child you can still be an amazing dad and not with the mother. If not the dad move on and be happy and find someone who respects you.

Hope this has helped in any way