Most Helpful Guy
Why would he do this to you? Because he is concerned about his own immediate gratification and doesn't care about your feelings or emotions at all. He takes priority in his mind and you are clearly slotting into the 'good times' category. If he has done this to you twice, you are permanently in there, unfortunately. That is not a category you emerge from to become a life-long partner.
Once a couple has broken up once, it will virtually NEVER work out if they get back together. You hear of one in a million cases where it does, but those have extraordinary circumstances. He has done this to you twice now, that 'one in a million' chance is pretty clearly a zero in a million chance. You are not the exception, you are the rule. That's obvious.
Giving him another chance was not really your fault, it seems like it just snuck up on you. But now that he has hurt you again you need to learn from that and realize that this will just become a pattern if you let it. You need to cut all contact, block him from everything, and move on. Don't accept a request a couple of months from now, don't accept an apology a couple of years from now. No contact. Move forward. Since it has worked once, he will always try. He will drop those little testers months later, years later. Just fishing to see if you are in a vulnerable state.
You have a right to be angry, what he did deserves your anger. Stop talking to him. Stop the snapchats. Stop it all. He will continue to hurt you.