Spiritually: Do you want your relationship blessed by God? If so, then be very careful how you act. Statistically: it something like 80% of people who live together never end up married (if that is what you ultimately want).
You should wait before moving in with a girlfriend shortly after a divorce. Waiting helps you know that you are making the right decision.
Yes, there is no law that says you can not.
No, you have no grounds to sue. You have suffered no damage by the girlfriend's pregnancy. Apparently, your divorce is in the works so you can't use the pregnancy as grounds for divorce. You should proceed with the divorce and get a child support order in place as soon as possible. Otherwise, you need to let it go and move on with your life.
You should probably wait until the divorce is finale.
Make a move
The divorce should have included a motion to this effect, otherwise not required to.
Find your next girlfriend and move on.
You should not. Just face it. you need to move on.
she shouldnt. she should get rid and move on.
Then the husband should move out.
Unfortunately you have to move on.
if you really love her
Move on, kick her to the curb, and find someone better.