You can pick the direction of not choosing a partner based on being pressured to choose. Don't get me wrong, I think the women involved have every right to insist on a commitment from you to be with them or not be with them.
You CAN step back. It isn't that you have a problem; you have a solution you don't like.
Incidentally, you wouldn't be the one burning any bridges. You're simply afraid that THEY will burn bridges. And they may. They have every right to. If either one of these women were to post here, I'd tell them both to walk away and not look back (except for child support and parenting issues). You're not ready for an adult relationship with either one, from what I can see.