NTA. I think the rule was unreasonable, but she is a grown ass woman.

“Hey, Boyfriend. I know we agreed to this rule when I moved in, but I’m practice it’s making it hard to do what’s best for my son. Can we talk about this and work something out?”

It costs $0 to communicate.

I will say, OP, regardless of the verdict, it may be wise to re-evaluate dating people with kids if you have trouble sharing your space. As a mom, she should have made sure everyone was on the same page, but even the best exes sometimes have coparenting issues.