Unexplainable feeling in chest? ?

It's like something is squeezing me in the inside. A dull sensation in my chest near the bottom of the ribcage. The sensation started when I had the coronavirus in April but initially it was a burning feeling that later turned into a numb feeling. I went to the doctor several times and they did blood tests and a electrocardiogram. According to the tests my heart and lungs are fine and I don't have clots. My blood pressure and o2 levels are also fine. I'm physically fit enough to go jogging and scale a mountain but the feeling never goes away. Sometimes I have headaches and nausea. Sometimes I wake up in the morning with heart palpitations. Sometimes I have fatigue. The feeling in my chest is uncomfortable and I'm at wits end. Can someone explain what could possibly be causing it?