You say "I didn't cheat on him or do anything with anyone for the reason that we were gonna get back."
Why would you break up with the guy in the first place... trial separation, freenight pass, lets chill for a few weeks... no matter what it is, this guy just done what most men would if they were alone in no relationship for more than a few weeks.
Either, suck it up and sort it out with him or, fuck him off and get with a real man that can hold you close & not let go... knowing what he has before he loses it.
Luck with your decision
