Hi, I had covid 5 months back. There has been a persistent problem in my chest. When I am walking or sitting, I feel normal. But when I lie on bed, specially when on back and when left side position, I feel little heaviness on my chest. I have had ECG, ECHO and treadmill tests done. All were normal. Can someone help me understand what could be the cause. Also, when I lie down the pulse rate is at 57-65.