Originally Posted by AtlanteanTroll
Okay, I'm sure I'm not the only person who will say this, but you really need some professional help. I had (have) similar problems, especially when I started college. With regards to feeling like you'd have less control than you do now, remember that when something like low self esteem, impostor syndrome, or depression is causing these sort of irrational, borderline delusional thoughts you don't have much control, and the therapist's job is to help you take the reigns back.
I'm sure other people who have gone through more similar things could advise you about talking to your parents. The only thing I can think of is to minimize it a little. Like "I'm going through a stressful period in my life right now, and I think going to a therapist/psychiatrist/psychologist would help me develop some strategies for dealing with it more productively than I have been." Depending on your circumstances, it may not even be necessary to tell them right away. It's okay for children of any age to keep some private information from their parents.