He slept with his flatmate lol

Bf of a year moved to college a week and a half before i did, ignored me pretty much all day for 3 days straight to "talk to her" but swore she was nothing to worry about then all of a sudden comes back saying he's lost feelings for me and I'm not the one he wants to marry anymore. Broke things off with me, I was completely devastated and just found out they've been dating for weeks and slept together and he's already confessed his love, great! So nice he cared as much as I did!!