Roommates BF ADVANCED level. Help!

I'm saying advanced because almost every route of complaint I have can be negated and it sucks. I live in a 2BR off-campus housing and just moved to a new unit over the weekend. My roommates BF has come over every night now and she gives him her key so he can come in and out as he pleases. This bothers me so much. I am basically always on edge because he can walk in at any moment and comes over literally every day like its his place.

Here's the kicker. We each have our own room, bathroom, and pay our rent completely separate. The only thing combined is utilities for the unit. Which makes it hard to argue he doesn't pay rent because I technically don't even pay my roommates rent.

Here's the second kicker: he has an apartment in the same building🤦🏾‍♀️🤦🏾‍♀️🤦🏾‍♀️ I feel like this just puts the nail in the coffin. He's just a few floors below so it's quite literally nothing for him to walk in and out of our apartment whenever he wants. He basically lives here. And when I asked a question he every quickly showed me the keys to HIS apartment almost as if saying 'you can't report me to the office because I already live here'

Please i need advice. I'm so uncomfortable but know very little will be done because management only cares about money and if he's paying his separate rent on time they have no reason to care that he's still violating our lease.

Here's the 3rd kicker: the lease says no overnight guests longer than 3 nights but he just comes in and out every few hours because he lives just downstairs. I asked my roommate about it and she flat out said "oh yeah he visits me everynight" and im like...

The 'EVERY night' vs 'OVER night' of it all is exhausting because it so nuanced and he basically lives here without living here.

I'm planning on having a serious conversation with her when I get home. Is it overreacting to ask to limit guests to 2/3 days a week and to send me a text heads up before he come in?

Just this morning I was in my pajamas making breakfast ( in shorts and a spaghetti strap) when he walked out from her room and left. I felt so exposed and uncomfortable I didn't even know he was there.

Am I overreacting? Please give advice