Ah yeah, no wonder why this is messing you up so much then. When you're young & haven't gone through the motions a few times already, every person you fall for is going to seem like "the one" & it's shocking when it doesn't work out.
I remember the first guy I ever went out with, I was head over heels "in love", thought he'd be my future husband, well that dream shattered quickly.

And even when I was older & I broke up with my last ex (who for about three years I was sure he was the right person for me, until I lived with him & got to know how he really is), I was really down about it, convinced myself that I'd never find someone new, no one else would ever be attracted to me, etc. But I was wrong, and those types of thoughts are never actually true, nor are they healthy.
It took me four long-term serious relationships to find someone who is actually right for me (not counting people I only went on one or two dates with). And I actually consider myself fortunate, some people take even longer or go through even more people, and there's nothing wrong with that.
You just gotta get out there & meet people, let it happen naturally, and stay calm/confident about it (again, easier said than done though).