Hi @Tarmac_6, welcome to the forum.
I know that fear. I was exactly the same when I was your age. I'm in my mid 50s now and have had some time to wonder about why I struggled so long with it back then. To be hones I struggled until my early 40s, but that's a different story.
Maybe some of this resonates with you, maybe not. I will say that at only 20, you're only just starting so I wouldn't be hitting the panic button just yet. If I could go back to my 20year old self and give him some advice, it would be to be yourself. If someone doesn't like your real self, then they're not the person for you. And don't try to be something you're not, just to please other people. If you have to do that then they're not the person for you.
So I guess, for me it was about being more confident. Not confident (that was always too much)... just more confident. Just opening up to people, getting to know people and most importantly, not wasting time trying to please people who never seemed to initiate contact. It took me far to long to learn that those people will never like me enough to be what I wanted them to be, so I should have just moved on and found people who would.
So it's hard to offer much more advice without knowing more about why you feel that you are in this position. It just takes some people more time than other people, and this could be for a variety of reasons, if like me it's being more introverted and lacking self-confidence, or it could be having higher expectations from others, or it could just be bad luck. Or a combination of different things.
You said that you don't know how to accept being ending up alone. Don't accept it. You're a long way off that happening and have so much time to find that right person. Just be yourself, like yourself, and never let that voice in your head (if you have one) convince you you will always be alone. There's only one person who will make that happens.