The Unknown

I've been having knee issues from running. Recently, I went to a Sports Medicine doctor. He concluded that it was from a weak hip, and gave me some excercises to do to strengthen my hip. I have been doing the exercises for two months now, and I have made some improvement. I still cannot lift my left leg as high as normal, and I feel a little unstable going down stairs sometimes. I've been running around 10 miles a week.
Feeling like something still isn't right, I went to my family doctor today. He is a great doctor. He spent over half an hour in the room with me. (Sorry to all the patients after me.) He did not come up with a diagnosis. But he thinks there's something wrong. I have muscle atrophy on one side of my body. It might possibly be a disk in my back or something else. I will be getting an MRI done on my back, and other tests done by a neurologist to try to figure out what is wrong with me.
I went in to the appointment thinking I would just get a referral for some physical therapy for my hip and knee. I've been a little emotional since my appointment, since this is not what I expected. I really hate the unknown. I feel nervous about what comes next. What if they find something wrong? What if they don't?
I know everything will be okay in the end. I know that Heavenly Father knows me and will help me through whatever comes next. But I can't help feeling a little nervous about the unknown.