How do I know if my HRM is wrong

Mamaincali

I have a Polar HRM that I bought 4 years ago. It wasn't cheap. My calories burned has always been high since I got it. As I lose weight though it is harder to keep the higher burn like it is when I am starting out all over again. I am 320 lbs, 5'6.5", 31 F and I am not used to exercising right now. I haven't exercised in months. I just started walking again last week. I am out of breath when I walk. So according to my HRM I burned 655 calories in 37 minutes. I don't know anyone who is as big as me who also uses an HRM to compare it to. I can't compare mine to someone who is 200 lbs.

In the past when I have exercised, in the beginning I start out high and as the weeks go on it takes a lot more effort to burn close to the burn in the very beginning. That's how its been the last 4 years with my HRM. It does sound pathetic that the last 4 years I have started and stopped getting healthy so many times.