I'm feeling really puzzled and a bit worried about these weird symptoms I've been having. My chest feels heavy on and off, and even though I've had loads of tests like ECG, echo, holter, TMT, and even a C-reactive protein test, everything came back normal. But then there's this pain in my arms and legs, with the left side feeling worse. In the last couple of days, I've also had some breathlessness. Eating and sleeping seem fine. There are these very brief chest pains that feel like an electric shock, just for a second. I've been trying to keep active by walking 5 km daily, but sometimes I find it hard because I get out of breath. What could be going on with me?