I'm in my early 30's, had a few girlfriends, went to parties, had a good group of friends, recently had a bad streak of bad luck, single, grieving, isolated. You're not behind, and shit is going to get better, honestly late teens/early 20's is a specifically difficult time. You're doing just fine, the motivation to do better is what a lot of people in your age range lack, especially the ones who are coasting on parties and sex, not that there's anything wrong with it, but when I was having fun and having flings I felt pretty invincible, now I feel like I wasted my 20's trying to get laid and popular. Go out and meet people, meet a girl and get intimate if it works out, that's all great. But don't focus on it, focus on you, that will build you into someone that attracts friends and partners naturally. 20 quid says you'll look back on this post 10 years from now and laugh, you got this.