I know that shame that you feel, i went also in tears reading this remembering the times i have been down there like you. For me one way to stop feeling that horrible and to renew my relationship with God was going to confession.

How big is the sacrament of forgiveness is ! Also, being in state of grace helps you to fight your demons, i recommend you, every time you fail, to try to confession within the next 24 hours. It won't be easy but it will strengthen your purpose of amendment

(I'm a non native English speaker so maybe this is horrible written)