i have had the same thing they are called palipatations it is a dramatic increase in your heart rate if you control your breathing youll be fine but still consult a physician the thing that helps most is sex. lol because palipatations are caused by stress or not eating properly.try to quit or minimize your intake for the next couple of weeks and then try finding a more mellow weed less of a head high more body high if this doesnt work you may have developed an alergy or could have smoked moldy weed there are a number of "ifs" so just try not to think about it remeber your mind is your worst enemy because it controls your body so if you think to hard it will happen again thats what kept happening to me anyway but hope you get through this man