Why can't I fall in love with anyone?

(19F) | have been loved by two men in my life and I didn't appreciate either or them. Both of these men were good people and healthy relationships. One of them I don't think I could truly envision a life with but the other I could yet I ended things out of fear that I would get bored of him because I was already starting to feel that way. I'm worried I'll never form a genuine connection with someone because I'll always wonder "what if there is someone better for me out there?". How do I change? I genuinely don’t think I’ve ever loved any of my partners who I felt would’ve loved me unconditionally.

TL;DR: I'm worrying too much because I feel like I can't fall in love with people who are good for me. What should I do?