Welcome to just answer,
Thanks for answering my questions,
Now looking at your age,symptoms,past medical history,it seems that your symptoms could be due to arrhythmia as that causes similar symptoms like yours so ask your physician to do EKG to rule this possibility out.
The reason for me mentioning this possibility is because when you don`t work or lie down the symptoms subside.Ask your physician also to do complete metabolic profile as imbalance in electrolytes like serum sodium,serum potassium can lead to arrhythmia and be the cause behind your symptoms too.
Other possibility could be thyroid
hormone imbalance as increase in thyroid hormone can cause similar symptoms like yours,so ask your physician to do thyroid stimulating hormone (TSH) to rule this possibility.
Now other possibility could be diaphragmatic hernia as it may present with gas bubbles in stomach and may produce heart symptoms too,so ask your physician to do xray of abdomen at erect position to rule this possibility.
Other possibility at your age,with similar symptoms seems less likely
Always ask if you need clarification/more information.Please click ACCEPT button to get my credit.POSITIVE feedback& BONUS are warmly appreciated. Please note that answer is for information only. It can't be a substitute to visit the doctor.