Are people born shy or are they made that way?

It was this guy on YouTube that talks about getting over shyness and low self asteem and he said ask youtsel why you are how you are he sai you its not genetic he said you are conditioned like that that's really the first time I thought about why am I like this I always thought it was gens but he said you are conditioned that way and I thougt about my life and how I got teased by girls and never had a gf cause my parents said I wasn't allowed to until i was 18 but all the other guys had girlfriends so I thought maybe I was ugly and maybe that's why I'm 18 now and have low self asteem and don't have any friends let alone a gf cause I would only get teased by girls cause I couldn't hit them I never got messed with by guys cause I would fight them and got into alot of fights but i was taught to never hit girls so when they would tease me I didn't know how to express myself verbally and i still dont so I wouldn't say anything and didn't know what to say and maybe that's where all my negative thaughts towards myself started since this guy said you are conditioned the way you are maybe that's why I am how I am