Thanks for your question on Health Care Magic.
I can understand your concern.
Breathlessness and chest heaviness in lying down position is known as
orthopnea.
Orthopnea is classical symptom of cardiac diseases like
heart failure, coronary artery disease (CAD) etc.
So better to first rule out these diseases.
Ecg can be normal in some cases.
So better to get done
1. 2d echo
2. Holter monitoring (24 hour continuous monitoring of ecg)
3.
Stress test (trade mill test).
4. Coronary
Angiography if required.
If all these tests are normal than no need to worry for heart related diseases.
Sometimes stress and
anxiety can cause similar symptoms.
So avoid stress and tension, be calm.
Don't worry, you will be alright.
But first rule out heart diseases.. Hope I have solved your query.
Wish you good health. Thanks.