Sorry about sounding like your wife...
Er....umm....
I'm guessing that's probably it!!!
You used to be working out and now you're not, but still eating the same...
Ding, ding, we have a winner!
Seriously, I think exercise is the key to weight loss.
If exercise feels too hard on your body, then you should focus on losing a few pounds by just eating better.
Then, once you've lost a little bit of weight 5-10 lbs., get started with exercise again...
That's what I did and I feel much better even after only losing 6 pounds so far.