Thanks Joseph for your reply! However, I had already tried what you suggested and it doesn't work (for me).
When I try the steps outlined at the link you provided and change the priority of the data sources that the Health app uses for counting steps, within a few minutes it ALWAYS resets the Apple Watch back to priority #1, and I have found that my watch significantly undercounts steps (not the least reason being that I don't always have my watch on...). You said you tried to change the priority on your phone - please change to something other than the Watch as the top priority, close the Health app then go back a few minutes later. At least for me, the Watch will be back at the top of the list, no matter where I just put it in the order. I've tried this a couple dozen times and the Watch reverts to the top priority every single time.
Also, though the article says I can tap the checkmark to turn individual data sources off, that also doesn't work - I can tap on the checkmark next to Apple Watch until my fingers bleed and it won't turn off. In fact, the only data source of the seven I have listed that I can actually turn off by tapping the checkmark is the Pedometer app I downloaded from the App store, which is one of the main sources I'd actually like to use. A bunch of old iPhones I don't even have anymore are on the list and I can't turn any of those off either.
So anyway, I very much appreciate you taking the time to try to help me but I think my problem will only be solved by some sort of iOS upgrade, or maybe if I get a new watch. :)