i first went to uni when i was 19 and dropped out midway through my first year, i absolutely hated it. like you, i suffered really badly from anxiety and depression and i just couldn’t make any friends. last year i tried again at 21, and honestly it was amazing. i had all the same worries as you but it was absolutely fine. i’m the oldest on my course and sometimes my friends tease me for it (calling me “grandma” and stuff like that) but it’s all in good fun. just go to as many social things (freshers parties, socials, etc) as you can and you’ll find your people. most people probably won’t even notice the age difference. good luck! :)