how to deal with the guilt of not treating somebody right?

We were together for about two years, a time that now feels like a distant, bittersweet memory. During that period, I treated him in ways that I deeply regret, ways that I know were hurtful and damaging. I didn’t cheat on him, but the lies I told him seemed to pile up, each one a brick in a wall that separated us further. I even resorted to stalking my ex, a behaviour that I am ashamed of and can hardly believe I was capable of. This led to him being behind in his academics eventually losing the chance of being in his dream college . Our relationship ended, and while it has been over for some time, the weight of my actions lingers heavily on my heart. Every morning, I wake up with a profound sense of guilt pressing down on my chest, a constant reminder of the precious thing I shattered between us. We were young and naive, caught up in the whirlwind of emotions and experiences that often accompany early love, but that doesn’t excuse the way I treated him. I find myself lost, unsure of how to cope with this overwhelming guilt and the sense of loss that accompanies it. It’s been two years since i did that, yet I am still not at peace. The memories haunt me, and I am plagued by the thought that I ruined something beautiful and irreplaceable. Even after our breakup, I attempted to move on by meeting new people, hoping to find solace and redemption in new relationships. However, I found myself withdrawing, isolating myself from potential connections because the fear of hurting someone else in the same way I hurt him, or worse, experiencing a form of karma that is even more severe than my own actions, paralysed me. The fear of repeating my past mistakes has become a barrier, keeping me from opening my heart again and finding the happiness I once knew.