The symptoms you describe are the exact same that I experienced last season.
I was doing 350+ miles a week. One week I did two centuries back to back. I thought I was getting stronger, but by mid season guys that I used to drop on climbs, were dropping me.The other problem was burnout before the season ended.

This year I have forced myself not to ride more than four days in a row ... take two off days in between (once in a while) ... and cut my milage down on days before I plan a long ride. At this point this year from last year I am at the same place, but feel much better on each ride, and I sleep much better. Oh, and I haven't been getting dropped during long climbs.

Lighten up ... it works.