Boyfriend of a year is probably cheating on me. I'm heartbroken.?

[Bibouse]

I feel so bad for you. I'm going through some stuff too, so I can relate to what you're going through. Here's my advice.
- Give yourself time.
And by that, I mean dump his sorry ass and give yourself time to heal outside the dating zone. Make plans with friends and family, pick up that hobby you always wanted to, exercise (great for the mind and self confidence.)

- Do NOT feel guilty about anything. BUT analyse what happened in the relationship, accepting that you might have made some mistakes, missed some signals that it was getting too bad etc etc.
As to how he could to this to you, maybe it isn't actually about you but about him. He's going through shit and it might make him feel manly and all that. So whatever you do, don't blame yourself (seen that too many often.)

As for trusting someone again, you have a choice to make. Two roads lie ahead of you. One is hate and the other is love. You can choose to keep your wounds festering and put a wall up, always being suspicious of new men, OR you can choose to heal your wounds and open yourself up. Yes, you might get hurt again, but you will never know true joy if you keep your heart locked up. Choose carefully but not suspiciously. eg no junkies etc...

Oh and to leave him, you owe him nothing. He has lied and used you. You owe him no sympathy, no consideration. Because if he won't tell you about a girl he chatted with, he certainly won't tell you if there is another one he had sex with etc. He might very well have cheated and not told you. Remember people with substance abuse problems tend to do horrible things under the influence.

Are you better off knowing exactly what goes on in his head? From personal experience, I will say no. There are some things you are better off not knowing. It will simply chip away at you. Assume it's over, leave him and take care of yourself.

Oh and here's a great line for kicking him to the curb - I know you lied, I deserve better than this. Good bye. (And if he tries to turn the tables on you, stand your ground. Stay calm. No matter how much hurt and anger you feel, keep it in check. Be the smart, cool headed one and walk away if it gets too much.)

PS: just for health and safety reasons, have yourself checked for std's. In case he cheated. Your body is your temple, protect it.