Heart problem? Well. please help me out!

My dad, age 64, has a gall bladder surgery 2-3 years back. After that, he has been having some discomfort in his chest, mostly in the side and below nipple area. He starts sweating immediately after that happens. Bec of dat hes getting scared nowadays given his age. He has done fasting and post sugar, it was fine. He has done ecg, thyroid, echo test, (that too multiple times), that came fine, after that he did ultrasound abdomen it was fine, just some growth on liver which the local gasentrologist said is fine. We have been to the opd multiple times, he's not getting any result. Please guide us what to do! I am doing wfh as of now, so he stays a little less worried, but once office opens m afraid he might panic! Please help us to narrow down the disgnosis! He also says he feels like gas below chest but he takes gas medicine as well. Please help me out!