What Causes Strain In Chest, Severe Cramps And Arm Pain?

Hi, I ve just come back from food shopping, while I was stood waiting for a taxi, I suddenly got this awful uncomfortable feeling in my stomach like I had been punched, and I could feel it radiate up to my collar bones. It made me panic. I have anxiety so me thinking about it more made it worse. Sat in the taxi and it gradually got worse then I finally relaxed and it stopped but now I have a lump in my throat like I would get if I m about to be sick. I had no chest pains when this happened an I could breathe okay I checked my pulse it was normal a little slow. Sometimes I get like a strain in my chest but I can t tell whether it s my heart on my chest muscles because it doesn t hurt its just uncomfortable. Depending what I m doing I ll get a bad cramp feeling in my left side of my stomach near my pancreas about a year I have been suffering from pains in my arm which the doctor had given me naproxen for because it feels like the pain is in between my bones it tends to happen when I get stressed or a typical day I m feeling low it ll appear in my forearm I don t know whether it my implant that s doing it or there s something wrong with my heart. I had an ECG the doctor told me that the morning I panic my heart rate go s up to 125bpm and I start to shake. I m 21 years of age, I am over weight but I started the gym an now have a personal trainer. I sound like hypercontriac but I m just so scared...