Hi Emily,,
I'm sure you'll find LOTS of people here that suffer the same. I am 26 years old and I am one of them, and yes the answer to your question is yes, the mind is a very powerful thing. You'd be surprised at the physical symptoms I have had,, and like you it all depends on the illness I am obsessing over that particular day. There have been times when I just couldn't cope with daily life.. Just flat out to afraid!! I was certain I was dying from something. It is a horrible way to live,, but try and remember that you are not alone, and that there is help out there!!
Have you gone to your doctor? Maybe discuss this with the doc, there are medications to help!! Keep posting
JEN