Lovebugg... what a messy situation. Can I be brutally honest here? Dump him. He's no good for you...

1. You're 18, he's 30, married, and has a child? I'm sorry, but he's taking advantage of you. I know you don't want to hear that and will probably vehemently disagree, and if he weren't married... I could possibly agree that it was *possible* that it was a sincere relationship, but... really, you're technically still a teen, and this guy has a wife/kid.

2. He's not good relationship material. He has a wife and child, yet is willing to "date" you. What that tells me is that he can't maintain a stable, long-term, committed relationship. He can't work out issues with his wife or make the decision to leave. Take this a step further... in a year, 2 years, 3 years... how do you think your relationship would be with him? Every relationship has issues at some point - if he can't work through those with his wife, you should expect that he won't be able to work through them with you either.

3. He's not good for your mental health. Are you already in therapy? Do you have access to a therapist? If you're having urges to cut, I'd take that as a strong sign that he's not good for you, and get out. Talking to a therapist might be helpful (in getting some clarity around this and in containing the urges?). But please, get out. Don't continue to reward his awful behavior (cheating on his wife).

Also, I don't think it's fair to say that you will hurt him by breaking up with him. He caused this. He is hurting himself, his wife, his daughter, and you. This is on him. He is the one that is breaking his vows and putting you in a rotten position. This isn't about you hurting him, this is about you deserving soooo much better, like someone who is honest, has integrity, will be able to fully be there for you (and not busy with their wife!), and can be an equal partner in a relationship.

Really, you deserve better and can totally do better.

Good luck.