Fear of love
Here's the deal: i was never very confident to begin with when i was growing up. i was never bad looking (not handsome, either), but i always was the VERY shy (and proportionately smart) kind of guy. didn't have many friends, and took me a shitload of effort to even approach a girl... they rejected me pretty much every time, usually in favor of someone more charismatic or better looking, which didn't boost my confidence.
long story short, a specific series of events in college started to change that. and that's when I met her, let's call her "Gaby." in retrospect i can say Gaby was the first person i truly fell in love with, and the first to ever say she loved me. except long story short again, Gaby and i shouldn't have happened. y'see, she cheated on a guy to be with me, and i knew that. then she cheated on me to go back to him, which i didn't know (she dated both at one time, i found out later). i betrayed many of my values, neglected important people, and did many other things i'm not proud of, to be with her. you might imagine i felt really cheated, abandoned and sad (though i might've deserved it) when out of the blue she just decides to break up with me and blame only me for "everything" (whatever she meant). it was frustrating, it angered me, saddened me and shamed me at the same time.
it's been 3 years and a half since that. slowly but surely, i've recovered most of my confidence. i'm driven, i have solid goals, i thrive at my job, i am assertive, i'm developing projects, i'm forming solid friendships, i've built a good relationship with my folks. the one thing i can't seem to do is hold a girl's attention for more than one date, sometimes not even that. i realized that still 1 year ago i was self-sabotaging, making excuses. still, today, i can't even formalize a date with girls i meet on tinder. i develop crushes that end up going nowhere because the girl in question usually has a boyfriend i find out about much later. and my mind goes back all the way to Gaby, the last time i fell in love and felt loved by someone, even if she was faking the whole thing. i feel trapped and unable to escape.