Post a couple weeks of training and diet log and let's see what the problem may be:
1. overtraining, you're not getting sufficient rest in between workouts
2. not enough diversity in training programme, too much distance constantly, or too much intensity constantly
3. not enough intensity in training, back off on miles and do more sprints & intervals
4. not enough carbs during ride and in recovery drink. This causes your body to disassemble good muscle-tissue to replenish glycogen-supply (ingesting protein will NOT prevent this if you're low on carbs). The inter-cellular amino-acid pool is only used to rebuild muscle-tissue after it's been catabolized; best not to have the break-down to begin with by not letting glycogen-supply get too low.