Heart Rate?

Ok so for the last half a year i have been suffering form a fast heart rate. Not all the time but allot of the time ( expecially after i eat) my heart rate jumps up to about 140 bpm. I have read that since i have allergies and asthma and take medication for both that this could be why (tachycardia?) Once it starts it takes a wile to calm down becasue of the anxiety that accompanies my fast heart rate. Does anyone know anything about stuff liek this? also im tall, in shape, work out, drink on weekends, smoke pot on occation, and im 19