I believe your build periods maybe to long. Depending on the time of year and the intensity my coach has me do 3 week builds at the begining of the season as the intensity is not as high and I don't have many important races, but mostly I do 2 week with a recovery week after. Also I get enough rest days in between in order to avoid over training. It looks like 3 week maybe to long for you, remember that you need to take into account life in general and any other stuff that may come your way.