I have a 20mi commute and I've been in a slump for most of the year. I'm not as active as you (can't stand running). I've averaged, honestly, 2 days a week this year. I blame the weather. It's been a grey, wet, miserable washout this year, and I've been totally demotivated by it (that and the flat scenery). Don't sweat it - just find a scapegoat and kill it.

My solution is to run away from mine