Am I allowed to be happy in a relationship I don’t deserve?

I have never really made any posts so if this is awkward and clunky I apologize.

So I (m22)cheated on a girl (f19 back then) about 3 years ago. And though it’s been a decently long time and I am no longer seeing them, it still eats me from the inside every day. So what happened was I broke up with a different ex (f18 back then) at the time and being my first relationship it really broke me and felt an emptiness without someone to date. So I almost immediately found someone else to date as a rebound. I’ll call her ex2. Anyways after talking with ex 2 for about a month(not dating, just flirting I suppose), I had to go to a summer program and reconnected with the EX1. So right before I left I asked EX2 if she wanted to be a couple and we got together. Anyways I get to the program abroad and ex1 is very adamant about getting back together, catching me alone, flirting, telling me things of the sexual nature. At first I tried to hold strong until I gave in and cheated on ex2. After that I basically just broke things off with both of them. It wasn’t completely necessary for this post to explain but thought it might give some context. Fast forward to the present and I am now with an absolutely amazing person (f23) who I love more than anything for the past year and a half. I do everything I can to make sure she feels loved and cared for. Only thing is every time I am happy with her I cannot help but think about my previous relationships. It isn’t like a yearning to be with them, quite the opposite. I keep thinking about how much I hurt ex2 and how little I deserve to be happy for what I’ve done. So I suppose what I’m asking you guys, does that ever go away? Is there ever going to be a point where I am allowed to be happy in a relationship despite the bad things I’ve done. I can’t possibly imagine I can do anything that could resolve me of what I’ve done.That being said I want to be the best person I can for my girlfriend and get past this so I can give her everything she deserves. I can’t stop thinking about it and have now gotten addicted to my phone because it’s the only way I can distract myself from thinking negative thoughts about myself. Of course I will listen to whatever people have to say, good or bad. That being said if you’re going to insult me, I can promise you anything you can think of saying I already tell myself every day.

TLDR: Cheated in a previous relationship 3 years ago and am not sure if I am allowed to be happy in a healthy relationship years later.