For the first time ever my heart rate became 50 bpm when doing an intense work out. Why would this be if I'm not someone that smokes or drinks?

There is a. reasonable chance that your method for heart rate monitoring is inaccurate and you have an incorrect reading. There are also disorders of the electrical conduction system of the heart that could cause this finding as well (rate related conduction disease) where the faster the atrial rate the slower the ventricular rate. You need to wear a reliable electrocardiographic monitor during exercise.