Hello, I´m sorry about your relationship, I don´t know what I should do in your case, but maybe I would try harder in the comunication, and have a pact with him in case he´ll do it again.
In that case maybe I wouldn´t forget him now and much less later.. This is about you, if you can live with that its ok but if you think sooner or later it will ruin your life...maybe you should leave him.
If you don´t forgive him now, someday you will be doing the same that he does; nobody wants that kind of relationship...it is supposed to be couple, partners.. if you dont have that, you will find it in someone else.
Right now you are young... what it will be when you are 60?? do you see both of you together???
thats the point... sharing life with someone that is special for you.....
Goog luck!!! Regards--