CC, One never know if they are telling the truth or not...but when she's far enough along a paternity test can be done to settle up this nonsense. I suspect he's been sleeping around and yes, w/her as well. Now the wait begins until such time as a test can be done.
I think you are wise in getting your finances and access arrangements sorted out. You can tell him that he's making a huge mistake, but he's not going to listen...he's on his path of destruction for now. The best thing to do is take care of you and your financial situation. You may even want to be physically checked out as well...just my two cents.
I'm sorry to hear this particular news, but it does crop up from time to time on the Forum.
Please take care of yourself.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.