Sounds like you are on the right track: a fitting and being mindful of resting when needed. Also, please be sure that you fuel adequately- especially on your riding days. I know I am most exhausted on the days when I did not take in enough calories during my ride.
Sometimes when we have lost weight and are still trying to drop some more pounds, we skimp on what we need to give our bodies enough energy to do what we are asking of it. Nancy Clark's The Cyclist's Food Guide can give you some useful information.
Great job with your weight loss and cycling achievements!
Grits
2010 Trek 5.2 Madone WSD, SI Diva Gel Flow
2002 Terry Classic, Terry Liberator