Sex drive isn't limited to testosterone alone, for example too high or too low estrogen could cause problems with your sex drive as well as a number of other things (like neurotransmitters, stress, etc).
In any case, when you cycle the excess hormones will cause your body to stop releasing LH/FSH. FSH is responsible for the reproductive aspect of your HPTA (i.e., sperm development). If I were you I'd spend more time looking into why you don't have any sex drive when you're not on high dose testosterone.
Maybe you haven't fully recovered from previous cycles.