I tend to feel really awful after I exert myself like that, too. Running for any amount of time makes me feel like I'm going to die--and it always has. In fact, I sometimes have a panic attack not long after exertion. T1 said I was the first person she knew who feels *worse* after exercise (thanks, T1--who still plays tennis at 70...).

T2, who is also trained in sports psychology, told me something interesting though. People who participated in sports/were otherwise very physically active when kids/teens tend to feel positive effects from exercise when they're adults. But people who weren't particularly active as kids (me, for example) often feel worse after exercise as adults, like they don't get the so-called "runner's high" or anything like that. It made me feel better for hating exercising (other than yoga or walking) and often feeling worse afterward.

Still might be good to get your heart checked out, just in case...