I get tired when I breath. Like, when I breath, my heart starts to beat so fast. I m 15 years old, and from time to time I smoke marijuana, but this happened to me even before I started to smoke marijuana. Down between my neck (throat) and upper chests, I can feel like some type of pressure, and sometimes even when I move from one side to the other side, my heart starts to beat so fast and I get this weird pressure in my chest/between my chest and throat/neck.
Thanks for your question on Chat Doctor. In my opinion you are having stress and anxiety related chest discomfort. Since you are taking marijuana, better to rule out cardiac cause. So get done ECG to rule out cardiac cause. If ECG is normal than no need to worry much. Your symptoms like palpitation (rapid heart rate),chest pressure and difficulty in breathing can be due to anxiety. So better to consult psychiatrist and get done counselling sessions. Try to identify stressor in your life and start working on its solution. You may need anxiolytic Chat Doctor.  And avoid marijuana smoking. It will only harm you. So quit as soon as possible.