Go see your doctor and demand a blood test to make sure everything is in order--hormones can be off, or poor nutrition will show up, etc
Good luck
Certainly not bad advice if persistent.
I would suggest perhaps too many days off spliced with too many long days. Mix it up. I ride hard twenty 5 mile loops during work week and longer rides weekends, 1-2 days off per week max. Make shorter rides worth it, do intervals one day followed by an easier spinning day.