I've posted a few times about symptoms which I feared were cancer, instead turned out to be cervical ectropion, overactive bladder and ibs but a diagnosed within the same 6 months. It was such a stressful time and I've developed severe health anxiety. I get to the bottom of one problem and then get new symptoms and have to start the process all over again. I am emotionally drained. The symptoms are all very real. Currently suffering with a constant unusual headache mainly on the right side of my head for almost 2 months. Never experienced a sensation like it. My left arm feels weak and I've had aching and pins and needles in my arms (mainly left) and at times weak legs. I sometimes feel faint and not with it. I suffer episodes of air hunger which have woken me from sleeping so I fail to believe this is linked to anxiety. I've had chest pains and fatigue. I could probably go on. So my recent concerns have been a brain tumour or heart disease/failure. Today, I have disovered a flat red blemish on my cheek. It is definitely not a spot or the start of, so I've spent the day googling skin cancer. 
My gp now thinks this is all anxiety after having numerous blood tests coming back clear apart from low ferritin but most recent check it was at 14 (up from 9). I really don't believe anxiety can make you this physically ill. The breathlessness and headaches worry me the most. How do I know if this is anxiety or that there is something actually wrong with me?