Unfinished buissness with this guy. (please help)?

Okay, so basically i was sorta seeing this guy nothing official but i was really into him and tought he was into me to. he texted me 24/7 from the moment i woke up till the moment i went to sleep at night. we hung out alot nd made out a few times nd he always told me how much he liked me. yesterday he came on facebook and said ''ive got somthing to tell you :/'' so i was like okay what and he said that hes seeing his ex gf again then said he was sorry nd felt bad. me being me just said 'thats okay :)'' i never really show my feelings and didnt wanna seem like i was too attached to him or anything. But i feel like i havent said enough last night i couldnt sleep cause i was so annoyed at myself i wanted to say more cause he really hurt me. the fact that i didnt say enough is buging me more than the fact hes back with his gf. but i dunno what to say to him or how to start a conversation. does anyone have any ideas to what i could say? please help :(