One party consent means only one party has to consent for it to be lawful. So that means if you're recording and you're okay with it, you're in the clear. Some states like California require two party consent, which means both parties have to be okay with it.

They're not married, so they won't share any marital/spousal communications privilege either.

/u/Throwaway16644432 death is not the answer. Do not kill yourself over somebody who doesn't want you. You have worth as a human and I know that your son does not want to grow up without you in his life. PM me if you want, I'm an attorney, I may not live in the same state as you, but I will help guide you to where you need to be. You can work on custody over your child and regaining your humanity, but you can't do that if you're dead.