I'm sorry to hear that you're going through all of that. Why do you believe that you're terrible at your dream job and how many credits will you be taking next semester?
And, on the relationship point: just because you haven't been into the dating scene officially yet doesn't mean you'll die alone. I had never been in a relationship officially until a month after I turned 21. It was February of 2017. And, I've had three relationships since then. Yes, three...that's a lot of dating experience right there. I'd probably be on the cusp of engagement if I wasn't so unlucky. Either way, while none of them ended where I wanted them to, I gained valuable dating experience and learned the kind of girl that I'm looking for concerning marriage and future and all that good stuff. Heck, I'd argue being late to the dating scene (but not too late) is actually a good thing...because you're more likely to run into someone mature now in college as opposed to high school. You'll get there...it takes patience and being persistent.
And if you're persistent and find someone kind, friendly, mature...a match for you, then who knows where it'll go? But you can't give up now...the worst thing you can do is give up.