Yes all tests has came back normal, thankyou for your advice and I will take it under consideration!
I'm sorry you're going through this.
Did your doctor do a full check up? Blood work and everything? If that all came back normal, that's great! I'm not a medical professional, so I can't diagnose. But I can tell you, the symptoms you described can be attributed to anxiety.
The thing about anxiety is there isn't always some "big stress event" that starts it. I know exercise can feel scary - if your doctor says your heart is healthy, then start small. I do a lot of walking - it's still good exercise that burns off the anxiety, but doesn't get you revving as much as harder cardio, like running.
Do you have someone you trust that you can talk to? Your parents, or a school counselor? The biggest thing we can do to help with anxiety is good therapy. This helps us identify our "triggers" and teaches self-coaching techniques to help manage the symptoms. For me, my triggers are big changes and exhaustion.
Be kind to yourself - when you feel these symptoms coming on, try to focus on things that help you relax and feel better. Call someone you trust and talk it out. Turn on your favorite music, a video game, or a movie. Get out and go for a walk. Try to avoid lots of caffeine and sugar.
Most of all, keep reaching out! Hang in there - hope you get some answers soon!