I have never had a girl like me. What can I be doing wrong?

When I was in HS I never had a girl crush on me; it was weird but I didnt care because there was always college; it wasnt any better. Now that I am older, I have few dates and most girls ignore me after the first or second one (but I do meet a lot of girls in casual envrionments, I also dont bombard with msgs). I sometimes get propositioned for , but nothing long term. I'm getting old and a lot of my friends are married, I am one of the few "holdouts".