Why did he break up with me out the blue?

My boyfriend of almost 3 years broke up with me out of nowhere saying the arguing was bad when honestly in reality it wasn’t. So he left one day later I see him friend requesting females on fb messaging them and telling them about our problems making me look like the bad one. I’m not going to lie I begged him for almost 2 weeks to please just drop it and come home bc I know he loves me well at least he showed it everyday even the night before he left the next morning. Anyways 3 weeks down the line I’ve cut the contact short now (but we did go to dinner and a hotel room last Friday and he asked if we could be friends I said no) but now when he drinks he talks to his friends saying f*** that b**** I loved her but I don't know (friends tell me this) that he wasn’t happy anymore etc when he was so lovey dovey never suspected a thing but also yesterday was his birthday and some girl on his fb said happy birthday handsome yes that made me mad why I don't know maybe bc yes we’re broken up but I still love him and don’t understand what’s going on. Can anyone clarify what kind of behavior this is. Will I get him back? 😔 he’s 44 I’m 37.
Why did he break up with me out the blue?
Add Opinion