>I just can’t help to feel like the nice guy, the guy girls settle with after being with a-holes.

Why is this phrased like a negative thing?

>I kind of wish I had had sex before her or something in order for me not to be jealous or frustrated.

Your jealousy isn't an experience issue, it's just a personality problem. You will run into this problem in future relationships no matter how many women you sleep with unless you figure out the core issue of what's got you feeling this way.

>it’s hard to love her with all these feelings and thoughts in my head.

Again, it's not difficult for you to love her. If that were the case you wouldn't be so confused on what to do, you'd just leave. It's not her, it's you. And because of that you'll feel the same way about anyone else. Break up, don't break up, either way you need to look inwards and get yourself figured out. Ask yourself whether that would be easier with a partner (care, compassion, comfort, someone to talk about your issues with) or on your own (peace, the ability to start fresh while you work on yourself). What do you need right now.