I think you need more time to recover. Try 3 times a week, increase mileage to 55 to 60, live in the big ring with low cadence for about a month. Put it into the lowest gear and stay anywhere between 14 to 18 mph all the time. Try doing the first 20 to 30 miles non-stop each trip. After 3 weeks of this i am getting marked increases on my overall mph(includes all stop signs/red lights). Went from 16.5 to 18.4 over my regular 53 miles. I am 66 years old. Love the wind.