Well, you are ahead of me. I came out of college thinking I knew exactly what I should be doing, started doing it, and was not until around age 30 I realized how lost I was, so congrats on some early life examination.You are so not alone in this, as a couple of other posters alluded to, such as adults are just large children with bills to pay. They throw different types of fits, want different types of toys, need different types of discipline, etc. This not feeling completely adult may never go away, and you may not want it too. When you've spent some time in the world you realize everyone around you is just getting by the only way they know how. So, don't stress about everything. If you go for a job interview just do your best, that's all you can do.(how does one adult, did i just not get the cheatsheet)
If you decide you want to go into some other career, my only advice is try to start doing it by around 30 y.o. It can get harder to switch each year after that age.