I have no friends and I can’t make any, please help

I’m currently 20 years old and don’t have any friends at all. For as long as I can remember I’ve never been able to make friends, in nursery I would always play on my own and enjoy my own company. Even through out school I had girls I would speak to but my friendships never lasted and they always drifted away or got new friends. I’ve always been left on my own. I don’t speak to anyone from high school or college. I always try to speak to people but I’ve come to the conclusion maybe girls just don’t like me. I actually spend more time with my boyfriend and his mates (they say I’m laddish and easy to get along with). This isn’t new to me, I naturally always make friends with guys very quickly and stay friends with all my guy mates but girls however just don’t stick. It’s really getting me down, it’s my 21st birthday in a few months and I’d love to have a girls night out but I currently don’t speak to a single girl my age. I work in a job with a lot more older people in their 30s and 40s and always get told I’m very mature for my age. Friends tend to leave me out because I’m not a huge drinker, I don’t do drugs, I have a boyfriend so won’t go to a guys house from a night out with them and over all maybe I’m boring? My boyfriend even took me away for my birthday weekend last year because he felt bad that i had no girl friends to celebrate it with. I just don’t know what I’m doing wrong? I’m not big headed or anything and tbh I think I’m very friendly? What do I do! I’ll never have a bridesmaid for my wedding at this rate and it’s so embarrassing when people tell me to go out with friends that don’t even exist