u/Actual-Horror496

I've had this problem for years. I feel so amazing working out at a gym, but even simple stretching on a mat at home (let alone actually trying to work out) gives me a dull headache, my heart races harder and faster than at the gym, and i'm not sure how to describe the feeling, but it's like, nausea adjacent? I don't feel like throwing up but my throat and stomach feel very yucky. Even if I immediately stop, the feeling can linger from a few hours to all day long.
What could be the cause and what might help me?