Forgive and Forget? Or Get out

I've been dating this guy for a year, tomorrow. And, I loved him more than I really loved anyone. We've been through more things than anyone I ever know! But, he's been lying to me. Behind my back he's been sneaking around to see girls, even my best friend! She is dating his best friend, and he didn't even tell me he was seeing her everytime he saw his best friend. And when I asked him he lied about it. He also told me to dye his hair then got her to do it! And then he told her he had a crush on her and would dump me if she'd dump her boyfriend so they could be together. But she said no. Then I found out. Then I hear my boyfriend, smoked pot! And lied to me about it! He's already on probation he'll go back to juvy if they find out! He lied about it all too, when I confronted him about it. I really love this guy. buy I can't imagine staying with him after this. I'm so confused on what to do, and my heart's breaking as time goes on. I want to forgive him but it's not easy.

Help!