Thanks for your question on Healthcare Magic.
I can understand your concern.
First of all no need to worry for heart diseases as your catdiac reports are normal.
Your pounding sensations are improving by putting
heating pad and taking
aspirin.
Aspirin is a good painkiller drug.
So possibility of
musculoskeletal pain is more likely.
So follow these steps for better symptomatic relief.
1. Avoid movements causing pain.
2. Avoid heavyweight lifting and strenuous exercise.
3. Apply warm water pad on affected areas of chest.
4. Take simple painkiller like
paracetamol or
ibuprofen.
5. Avoid stress and tension, be relax and calm.
Don't worry, you will be alright with all these.
Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.