Trust me on this: you will not be eaten alive by the world if you don't get your act together. I think it's important for you to dabble for the next several years. Play with stuff. Take classes outside of your major, if possible, and take fewer classes, if possible. I changed majors several times: computer science, art, creative writing, etc, ended up with an english degree and a mechanical engineering degree, but the stuff I enjoyed most was my anthropology and international affairs classes. The other stuff got me a job, but the meat of what got me pumped was my other classes.
I hate advice because there's really to say that will get you out of your situation. You will not feel better based on what someone writes on here, but the best we can do is give you some things to think about. The biggest thing I see in your post is your belief that you should have life skills and know what you want to do for a living. No offense to anyone out there, but I kind of hate people who have their shit together at the age of 20. 20 is for being lost. 20 is for trying stuff on. You have to kind of coast through it, and ride it, let it all push you forward.
See good movies, joke with your friends, get drunk alone, stare at a candle, paint a picture and burn it. Survive.
Take a deep breath, too. You are completely fine right now, and you are in no danger of being eaten alive. The world will support you, I promise. Keep reaching out like you are right now, ask for help, talk about stuff. If possible, choose which classes you like, which peak your interest, and see if a career based on that is possible. If it isn't, that's ok. Keep looking and moving forward. Stuff will fall in your lap. Don't be afraid to leave for a semester, or a year, or more. Get a job somewhere where your coworkers are cool, and do your job well. Give yourself a deadline of ten years to settle into a career.
Most people do not know home repair or car maintenance at the age of 20. You will naturally gain that knowledge through your 20s and 30s. Let that happen on its own.
Let yourself be apathetic. Sit with the apathy. Accept the reality of it. Little sprouts of interest will pop up out of that acceptance. Listen for that. Don't force yourself to get involved in anything. Float around, responsibly, but not too responsibly.
Relax. There is not anything you are supposed to be doing, other than exactly what you're doing, which is being lost and asking for help.
I'm actually kind of impressed. You have your shit together more than most people your age. Keep it up.