I had this too (just about 15 minutes ago actually). I was running to the store before it closed, and 1) my lungs started to hurt, but mainly, I had a taste of metal/iron in my mouth, my gums felt itchy (or like I needed to rub them), and I was producing so much saliva that I had to constantly spit. I didn't feel faint, but I did feel a little more light headed than usual. It's winter here, about -5 Celsius outside, I think maybe that had to do with my lungs hurting, I was taking so many deep breathes that the cold started to actually hurt when I would inhale. I've never been diagnosed with asthma, but I've always suspected that I had it, even if mildly.
Would love to know what the metal/iron taste was though.
I kept checking to see if I was internally bleeding or something.