I go through times where I exercise and eat well for a while and lose steam when the payoff isn't there. According to myfitnesspal, I typically have an extra (edit) 1100 calories I could consume each day and still lose 1 pound a week. I'm +4 pounds for the last 2 months (and still feel hungry since I'm eating less) :(
The good news is I've been exercising for the last 2 months and haven't quit yet. This makes me healthier... I just need to find out where the weight is hiding. There are many variables here so its a much longer process than I would prefer.
What changes things a lot for me is finally forcing myself off gluten, which sucks cause I like beer (the Widmere Omission line is gluten free and really good, just a bit pricey), I could literally do everything right and if I ate too much stuff with gluten (like bread, I love toast and honey and fancy sandwiches both) and I'd never lose an ounce.
Kicking gluten also made me less hungry, I forget to eat about half the time now. I just had surgery so I'm not even exercising beyond opting for walking places over driving and the like.
I don't have what you'd call Celiac Disease (which is pretty severe), but doctors have been bugging me for years to go GF or very restricted, I knew they were right, but it's a pain in the ass. On the upside you pretty much will have to cook for yourself more and that's healthy and satisfying for most folks. This is the first time in years that losing weight was "easy", or at least comparatively easy. I'd guess gluten was slightly inflaming and fucking up my gut somehow, which caused all manner of issues.
I'm not suggesting your gluten intolerant per se, but if you find it harder than other people to maintain fitness, you might have some kind of dietary issue. Eliminate the obvious ones first, gluten, lactose, and then casein, see if that helps.