Should I break up with LTR of 15 months total because I want to sleep with other people?

Background: I'm 19, she's 20 and we're both in university. I cheated on her once and we broke up for a few months while remaining FWB, but then we got back together, and it's been half a year since.

She's an amazing girlfriend when she wants to be, but I've caught her in lies before.

I'm troubled because I'm not done maturing as a man yet, and I feel like I'm not at my full potential. In the past, she had tried to stop me from working out because I would get "too attractive." I also feel like I'm missing out when my friends are going out and I can't do anything.

I think about the single life and how fun that would be every few days, but I can't help but think I might regret breaking up. I also do really care about this girl, and I can't bear the thought of breaking up with her and hurting her again.

Thoughts?