I'll sum this up as quickly as possible

>date girl for a while
>breaks my heart
>left a scar making me think I'm undeserving or that any happiness isnt real
>start dating girl
>in love
>always lash out at her because I get these bouts of low self esteem

This bitch hurt me so bad that I think I'm undeserving of anything and I feel like it's going to hurt my relationship now. My girlfriend is understanding but I know it takes its toll on her having to deal with my bullshit. How the fuck can I stop being like this?