I think I have some kind of a mental illness
Oh no, really? Why do you think you have a mental illness?
It runs in our family, my brother has manic depression
You need to seek help if you have fears about having a mental illness. Just because one family member is mentally ill does not mean that your are too. Admit to your fears and work on getting past this.
I'm going to go ask my friend for help.
It's good to have a friend to help you, but you should also seek some professional help as well. Mental illness can be a very powerful thing.