Why do I (18M) feel jealous of my partner's (17F) success and accomplishments?

I'm a 19-year-old male who recently ended a relationship with an 18-year-old girl, and I'm reflecting on what went wrong. We met while I was a senior in high school and she was a junior. A key issue in our relationship, ultimately leading to its end, was my jealousy towards her. She was a cheerleader, an honor student, a flag football player, a student ambassador, and a track athlete. She consistently brought home honors and accolades, and instead of feeling happy and proud, I found myself consumed by jealousy. I struggled with feelings of inadequacy, believing she was a better athlete, student, and teammate than I was, which fostered resentment in me. I couldn't shake off the fact that she had won a state championship in cheerleading the year before we started dating, and even though I truly loved her, my emotions overshadowed my pride in her success. My reactions were unhealthy: I stopped attending her events and undermined her achievements, both in my mind and openly to her. I realize now that these actions deeply damaged our relationship and made me feel like a terrible partner and an even worse person. I find myself asking: Am I broken? What’s wrong with me? Why couldn’t I just be happy to be the person she chose? I understand I was in high school then, and now I'm in college, which might make my struggle seem trivial to more mature individuals. But I’m seeking advice because my jealousy cost me a wonderful relationship with a sweet girl, and I want to understand how to address this issue within myself so I can grow beyond it.