Cheating on partner with love of my life

My ex broke up with me last year and I started dating someone again, he was sweet and kind and a little immature and we had communication issues here and there after our relationship became long distance. My ex contacted me to be friends and we stay in contact with each other for a while, I never told him I was in a relationship because part of me didn't want him to know, I wanted him in my life in any form or way and I was afraid to lose him (I clearly wasn't over him in hindsight). When my long distance partner moved back to their country I tried to be faithful, but with easy access to my ex, my LDR relationship reducing to barely any effort on both sides, and COVID-19 (I was taking it seriously and not seeing anyone, I became depressed and lonely) - I started seeing my ex again and it became a full blown affair. At this point I don't feel like I have a right to either relationship and I don't deserve any forgiveness. My depression has not improved perhaps because this affair has always been in the back of my mind. I don't know how to tell them. If anyone has cheated or lied, or if you just have any guidance on what to do or say. I would greatly appreciate it, I need to move forward and stop harming other people.