Unfortunately, it’s impossible to tell parents that you are all grownup and be believed. You have to show not tell, and even then, your parents may still see you as their little baby.
Here’s a clip from Steve Martin’s Father of the Bride showing what it looks like to Steve Martin’s character when his daughter announces that she is getting married (the funny part is at the end):
youtube.com/watch?v=qdQb7p3FQOg
I don’t think your parents can help you with your college right now. It’s possible that they could if they had some relevant skills, but the way you describe it, it sounds like they really want to help, but they can’t. They can’t go through college for you no matter how much they want to–you have to do the work. There’s no getting around it.
There are areas where they can be helpful to you, but 95-99% of your problems ought to be solved on campus. You need to figure out what are college type problems (to be shared with a student counseling person, a professor, a friend, a chaplain or an RA) and what are mom and dad issues. It isn’t a mom and dad issue if mom and dad can’t fix it.
Good luck!