Pretty damn sure I just lost the love of my life.

Being more of a silent observer of the OT I never expected to be posting on here but I'm in need of some honest anonymous advice on women.

I met the woman I expected to marry and conquer the world with we've been dating over two years and shes put up with me messing up more than once and I can see that she's done with me.

Now I have no doubt in my mind that this woman is well worth it, good fun family, smart as they come, goal oriented, beautiful, active, kind, generous, tight body, fun time, cultured, gives bj's fit for a god, I can go on for days.

However I'm 25 and have been messing around because I thought settling down was years away and they'll always be more women, and although shes forgave me many times before I can tell this times different.

Now I've suddenly lost interest in fooling around but its too late.
How do I prove to her that those days are behind me?