Maw, you have my sympathy and empathy too! I am like you - just had a very good NHS m.o.t. in every way, except for weight - sigh!
I have been very sedentary for the past 6 months, firstly through ill heath and then through habit. I have bursts where I try to conscientiously reach the '10,000' steps target, but if I do not go out, that is hard to achieve, short of walking in circles around furniture and up and down the stairs for the sake of it.
As a sort of 'mini' exercise routine, I do make a point a couple of times a week of going up and down said stairs until I have reached a count of 1,000. Boring, but it must help! Maybe this is the way to go (though not if you live in a bungalow ha ha!)
I don't have a stepometer - or whatever it is that you use to count and I know this fad of trying to ensure you do 10,000 steps a day is now on thw wane and we are into the '10 minutes of BRISK walking' instead. But somewhere within all the different bits of advice is that simple ' get moving' idea.
Maybe the simplest thing for you will be extending your walks with the gorgeous Hattie at your own time and pace.
I know I have slowed up. I am hoping that getting back to full-time work will now make a good difference especially as some elements of the job will be physical.
The very fact that you are thinking all of this through is a good thing, I am sure, so good luck and let us know if you find a way/s to make a difference.
Incidentally, I used to have a dog called Hattie - 57 varieties with a fair bit of collie and mad as a box of frogs! I think I was at my fittest then, walking her along a stretch of local beach every day. Power to you! xx