How do you tell someone how bad they smell without being rude?

My roommates boyfriend is constantly here, whenever he sleeps over the smell in my room becomes unbearable. i have actually had to leave because of how bad it smells. i do not want to be rude and say he can’t stay here especially because if hes not here he has to travel 3 hours back home, but i would really like to either cover up the smell or get rid of it without being rude. i’ve tried febreeze, candles, then air fresheners (oder eliminators), we even have a air filter. he showers but obviously not as often or as well as he should.