Your "baby momma"? I thought you were M, so why refer to her as though she had your kids illegitimately?
Frankly, I can't blame your GF for wanting out of that drama. And, yes, you have shown very weak and unattractive behavior. IDK, some guys just never learn. It's not the fault of your divorce,.....it's YOU.
Having kinky sex on the second date and quickly moving in together (with a house full of kids).......when each of you are on the rebound of divorces, spell disaster. If she's running for the hills, be thankful.....and pray she's not pregnant. But if she is......then you can call her your baby momma.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!