Dreams and second chances

As much as I want him to follow his dreams and pierce and tattoo, I don't trust the women who want to have those services done by him. I wish I could tell him he can only work on men but that will never happen... though it's close to a year since he cheated on me I've been worrying about it more and more lately... he swears he hasn't cheated on me since and never will again but how can I trust him?
I once gave him permission to sleep with another woman if I wasn't enough for him... apparently 4+ other women weren't enough either, because he bragged about it all the while. I worry that he'll go back to how it was our first 9 months together and I'm scared shitless. Not only did he sleep around and brag about it, he treated me like shit. Like I was a lesser being. Like I didn't deserve him and would never earn his trust and love, which he should've been fighting for from me, not the other way around.
I know I would leave him the instant I ever discovered that he was lying to me or cheated on me again, but I hate that I worry incessantly about it and fear that each day I have with him may be our last.
Why I chose to stay with a cheater, I don't know. I never thought I'd be one to give second chances for something like that. I wonder what kind of mentality I've built up after being subjected to all of this...
I want him and I to chase our dreams together but I fear they will one day lead us apart. Some day my love for music and his love of easy women may tear us down and pin us against each other...
I love him, but I have fear of our relationship. I sincerely hope that this relationship is leading down the path of our dreams together and not down the path of our doom...