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.