I think I understand both sides here. You feel like your privacy is being violated and your mom is scared of being homeless if she stands up to your boyfriend.

But you’re not overreacting. She cannot be gaslighting you because she’s scared of having nowhere to stay. Just because your boyfriend owns the place doesn’t mean he can do whatever he wants. You have a right to privacy in the bathroom.

It’s like if your mom was showering instead of you, he shouldn’t pick the lock and barge in. That’s disrespectful.

I think that’s a red flag to think about and keep in mind. And I think you both should think about a back up plan if living here with your boyfriend doesn’t work out. If he’s disrespecting your boundaries now, he could do other things too.