You could be getting diaphragm cramps - I sometimes get these if I work really hard without warming up properly first (or have cooled down rapidly - like descending on a cold day - then climbing again hard). They don't really feel like the muscle cramps you'd feel in your legs to me - it feels more like really really intense menstrual cramps, but higher. Stopping will make them go away.

and btw - don't get too upset about really high hr's we're all different and some of us run high. My measured max is 211, which while higher than many people's is still quite safe and normal and some people go even higher than that. (do watch though because sometimes really high numbers can be caused by interference from things like invisible dog fences, induction loops at stoplights, power lines - I know if I see 230 its one of those things and not me)