Weird symptoms with breathing, not asthma?

For some reason, at random times, my throat feels like it's closing, and I can't breathe. It doesn't happen too often, but it's never when i'm exerting myself. And I can see my heart beat, and at these times it beats almost continually, like a dog panting. I don't breathe faster, I just can't breathe. I don't think it's a panic attack, because nothing special was really happening then, but something is always happening, so I'm not ruling it out. And I'm 16, if that means anything.