Break up ? please help

Megan
My ex and I have done a lot .. And he's seen everything of me and I've seen all of him.. We've only been going out for 3 months but I really felt something .. But one day we didn't really talk and I was confused (two days ago) on the 4th and I look at my phone that night and he simply said 'we need to break up' I didn't understand so random and just seemed so heartless.. The. He asked for a two week break and I said 'that's just a two week window for you to go hook up w/some girl and then come back if u felt like it. You can either stay w/me and resolve this or you can leave..'
All he said was 'bye I guess' 
I lost it ? I didn't want to loose him he became my everything.. My whole world revolved around him..
His reason was because 'he wasn't happy' ? what was I doing wrong?! 
Thank you for reading please comment..any advice helps ? sorry ra sonlong