Hi there - sorry you are feeling anxious. It's not a good place to be I know. However, your GP is the expert not Google & not you either. You say you "can't help it". Actually, you probably can help it. It seems to  me you have 2 choices. (1) take what your GP says as true & just be a 17 year old with your own healthy life ahead of you, or (2) carry on spoiling your life by worrying about things there is no need to worry about.

There really isn't a third choice is there? You need to keep busy doing all the healthy, happy things that 17 year olds do & focus on those things not on your health. I don't mean to sound harsh or cruel 'cause I do understand about anxiety but you must find a way to be realistic & think carefully about whether or not you want to spoil your life this way.

I expect you'll make the right choice 'cause you sound like a nice, intelligent young woman to me. x