You know, Oakleaf, I think it could be a nutrition issue. I have recently found that I need to eat a Luna bar before even one of my short "after work/out of time" 15-18 mile rides, or I really feel like crap. Since all of my rides from home involve a mile climb at the end, I am spent after that. And yes, I rarely feel hungry on a ride, but if I don't eat a lot, I feel worse. My friends seem to exist on 1-2 bars and a pbj sandwich, with some type of sports drink on our 30-50 mile hilly rides, but I think I need to do more. I am wary of eating too many calories, but it's becoming more and more of a problem.
I still want to work on my strength, though. I can barely get myself to stand on my pedals, which is why I had to walk part of the 20% grade in Connecticut a couple of weeks ago. When the others stood for the last hard part, I gave up. And that's something I don't often do...