Does anyone else think that the symptoms that they are feeling are something life threatening?

If I have a stiff neck I think meningitus,
strange feelings in head or headache I think brain tumour or stroke,
racing heart or sharp pains in chest - heart attack,
strange vision - tumour of some sort,
pain in leg - blood clot.

My main fear is getting cancer.

I get lots of different symptoms, some more than others and I always think it is something deadly. I try to challenge my thoughts and convince myself it is anxiety/panic but nothing seems to work.
I have been to the doctors but they just say "oh it is panic". I dont know what to do.