Going through school is hard. Whether you are graduating high school, or college at this point it's difficult to know exactly what you want to do after it all. From our teenage years we are expected to know what we want to do with our lives and what our plans are after graduation. Do we go to college, not go to college, go to graduate school, get a real job, etc.? What happens if you don't know? Guess what, that's okay too. People just won't tell you that because they think you need to rush everything. That's not the case.
It's quite alright to go into your undergraduate education undecided. Go there take a bunch of different classes see what you like take more of that, then you can decide. It's okay to play around with different options to find out what you really want to do.
Personally, I have my major decided on, and I still have no idea what I am planning on doing with it. There's nothing wrong with that. Many college seniors that I know either have their lives figured out or they don't. And that's not a bad thing. Some want to go to graduate school, and some are dipping their toes into the big bad world and getting their "real world" jobs. Neither one of those people have their lives completely figured out, and certainly didn't when they were graduating high school.
You'll go through major changes after graduating, but that's a great thing. Don't be afraid to change your college major a couple of times before you find the right degree for you. Don't pressure yourself into picking "the right degree" either. Just do what's best for you and what you love the most.
As for after graduation, everyone has no idea what they are doing with their lives. It's a hard decision all in it's own, but much like figuring out what you're doing with your education, just get into multiple things, try them out for a while, then see what you really like doing.(For example) Maybe you love that job that you got after getting your Social Work degree, but you also like doing people's makeup on the side. Keep doing what makes you happy, and worry about the degree later.
It's okay to not have it all figured out, but what's not okay is sitting around and not doing anything while wallowing around waiting for the next big thing. No. You are the next big thing, get over your nerves and try everything and anything out there, and you'll never be afraid of the "not knowing" ever again. Graduate with pride, then try, succeed, and fall in love with you and what you like to do.