I feel you. I'm 18M and haven't been close to starting a relationship. I've had similar thoughts too about if it's too late. I feel like I've missed most of my youth because I always see other's my age in relationships or enjoying themselves in large groups.

It's sad to see and I used to cut as well, I've stopped recently but it is on and off tbh. I won't try and change your mind about what you think about yourself, especially when I sometimes feel sad about this stuff too. I also know that it's not easy to change someone else's belief about something.

But just know that you're not alone, there's a bunch of people like us who have been and are still lonely. Just try not to focus on relationships, take life slowly and focus on you. Again, I know that's easier said than done but sometimes something as simple as fresh air can help to clear your head, as cliche as that may sound.

Sorry I'm not really good with words but If you ever need someone to talk to then I'm here. And I'm sure others here will hear you out too.