It's okay to be mad. Especially after knowing you invested so much of your time in the relationship to not understand why he kept it going for so long. But don't allow this to emotionally affect you in a way that it drains your energy.
Don't try to put in perspective why it ended or why he was a jerk. Don't concern yourself with questioning why some people do foul things to others. It's going to hurt right now, but eventually you'll be thankful that he has shown his true colors before you wasted any more time.
Talking to him won't help. You may feel like you may get some closure and the answers to your many questions out on the table, but truth is, it's an overrated process. It isn't going to make you feel any better, and honestly, you won't get it in the emotional state you're currently in.
I'm sorry if my words sting a bit, but this is everything I have learned & wished someone had told me. I wish you the best.
