mind feels unworthy to make gains

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19 year old here. I used to play a year of high school football when I was 15, and I was required to do the workouts, especially in the offseason (I think it was crossfit). along the way, I realized I was wake than my peers who started a year before me, so because of that feeling of inadequacy, I stopped going over time despite my body getting much bigger and stronger and less chubbier. I spent 10 days away from lifting and loss a lot of muscle mass. my mom then had me not go to football camp (which is an important place) because of my Latin grades and my poor football attendance at the end of the year. when I asked my former coach junior year if there was potentially a chance for me to come back he essentially Saud no, that door is closed. I felt weird, and I tried doing wrestling to grow over it but that didn't work out either. I then realized that whenever I try to build my body, I fall off, because my former teammates got their immense size through football, where as mine would have to be earned back.

TL; DR
as a shunned former high school football player how do I get over feelings of inadequacy to make gains and get big in muscle again?