Ask around and see if anyone knows if no one does see if he acts wierd or maybe different,or you could just ask him
You guys need to talk about this and consider your options. Goood Luck!
how do you know if your boyfriend has cheated
Sounds like you need a better boyfriend.
Next Boyfriend....
obviously that person is going to deny having a fling with your boyfriend
Well think about who told you. Was it your friend? And where did she hear it from. Try to find one of your boyfriend's past girlfriends and ask them if he had ever cheated on them. If he is a cheater try to find someone else. It's best to be with someone who you know isn't going to break your heart.
tell her that her boyfriend cheated on her. she needs to know.
Let him have her, and find yourself someone who respects you.
Dump him
you go and tell him you cheated on him and tell him how sorry you are and ask him to forgive you.
There is no way to positively know if your boyfriend has cheated on you unless you catch him or he tells you. There may be some signs such as not being where he says he is or lying to you on who he was with.
This can only be determined by a DNA test to find out who is the father of your baby. Unless you are willing to do this (and your boyfriend or any lovers you have are willing to be tested) then don't blame your boyfriend.