hi , i am 30 , if i stand up a bit too fast or something similar i can fell my heart pumping in my chest and change rythmn and people get little pains in their body and because of the heart changing rate and i can feel the pressure i get worried also about little pains in left arm when i get them but this might be my sleeping position but still i get worried about the heart thing if its A F atrial fib or something similar , ive been taking a low dose aspirin just in case and am making doctors appointment tommorow , i do not drink but smoke sometimes and am overweight but not obese im 6 foot and around 15 -16 stone i think , i am going to radically change lifestyle and diet and exercise , but am hoping you could share your insights and perhaps help calm me down a little as when i think about it i get stressed and panic a little , thanks , p.s im on a low dose of medication for previous opiate misuse ,but havent used any class A substances for years