I can relate to this and when I was your age I had the same thoughts and the were two things contributing to them...
Like many people have already said, you are still very young and you’re being too hard on yourself. Try not to compare yourself with others especially through social media. It’s a lie. You are not as “far behind” as you think you are (and maybe one day you’ll realize there is no competition and there is no scoreboard but that’s for another thread)
You may need to seek out a mental professional. I thought my anxiety and self hating inner monologue was due to my lack of life success but it was actually the other way around. I had some anxiety disorders that made it impossible for me to focus on anything besides the panel of judges inside my head critiquing and criticized my every move. Once I made this my top priority and got my mental health situated, life just seemed to slow down. It was only then I could concentrate on what was in front of me and start accomplishing goals whether they be relationships or career.
You already did the hardest part and admitted that you don’t have the answers and need help. Good luck I’m rooting for you.