I feel like i may be having heartburn? But i have never had it before?

I feel like i may be having heartburn? But i have never had it before? I am 18 years old and for the past couple days especially during the night my chest feels almost as if a 400 pound man is sitting on top of my sternum and i really cannot breathe. I started taking Prilosec OTC yesterday and regularly eating TUMS which has helped minimally. Do you think this is heart burn?