I feel like my heart keeps skipping beats?

Well for starters im on 90 mg of adderall that i popped at 830 so if i were to overdose it would of been forever ago. But anyways i feel like it might be an anxiety but im not sure cus all i can think about is my heart stopping or a heart attack, or some cardiac arrest ****. my heartrate is 76 speed per minute on a resting heartrate, the thing thats bugging me is that im breathing so hard constantly to try n get air cus it feels like im not getting any and now my chest/heart/back/neck hurt really bad and that's just adding on more anxiety... im subscribed to clonezepam but i dont want to mix a downer with an upper