For the past week i have been having some discomfort and mild pain right in the middle of my chest or on the right side of my chest. The first type usually occurs when i am lying down or sitting. Like there is some pressure in the middle of my chest and i also feel my heart beating hard. The second type on the right side of my chest but still close to the middle, is different. There is discomfort when i breathe, especially when i exhale. I don t experience both at the same time but both cause my heart to beat or palpitate harder than usual. I m guessing this has something to do with my heart since it makes my heart palpitate and i am also a heavy smoker, I smoke 2 or three packs a day and have one beer with dinner. no there isn t pain in my left arm. the first few times i sat and waited for pain because i thought i was having a heart attack but it never came. Also, i am not panicking from the palpitations, i quite like how they feel actually. i am 23 years old.