Feeling down in the dumps because it's my birthday?

What's the secret to making friends if you have bad posture or socially awkward? I don't want to bbe popular but being alone on your birthday kinda sucks ESP being 21. Help? I admit to my mistakes of fear of not being rejected but I got over that my senior year.( had a gf for six months but I felt she was too young and I was too mature for her.) but after it started to creep back in like middle school.(being bullied by popular kids BC I wasn't like my older brother) I also am trying hard to be persuaive and not look disinterested but it's hard :/