Stuck between long term partner(ex) and new parnter - HELP!

[So_stuck_and_sad]

I will try keep this short.

I was in a relationship for 3.5 years. We were best friends. Things started to change and I had a feeling in my heart that I wasnt happy. We were always aruging, never on the same page and I knew that my feelings were changing. I wasnt sexually attracted for a long time and he deserves to have someone that wants to have sex with him! I feel like I outgrew him as he can be super immature. I started falling for someone else that was also in an extremely unhappy relationship (worse then mine). He left his partner and I left mine. New partner has been amazing to me. His ex moved on straight away also. My ex wants me back all the time (he doesnt know about the new guy). I dont know if I made a mistake. I know I was so unhappy and he did a lot to push me away but I think I should have tried harder. I love both, but they are both so different and I see my life going in complete different directions with each. I know I would be happy with either one but maybe more happy and suited to my new partner. I feel like my ex is my home, but my new partner is more suited to me. I cant stand the thought of my ex being sad and alone. Everything I promised him I have now taken away from him, (buying a house, marriage, kids etc). The guilt kills me. It consumes me every day so bad sometimes i feel like I cant breath. I go to a psychologist once a week but im still so stuck. I just cannot make a decision. My new partner can feel my guilt and my confusion and it hurts me. He treats me so amazing he doesnt deserve my indecisiveness, guilt etc either. How do I make a decision? Even if I did go back to my ex theres too many lies etc now isnt there? How do I stop this from haunting me for the rest of my life? Or will this be my karma forever now? Sorry for the long sob story 😞

[So_stuck_and_sad]

It has been over a year now since this has all happened. I still feel so anxious about the entire situation. I know I made a mistake.. Leaving him for another man. Even though im still with the new man, and hes amazing to me. It will always feel wrong in my heart. Is it possible to let go of the past and move forward when you have done something this bad? I cant ever see myself being 100% happy after what I did.