Hi SamjW - usually the advice is to continue taking the Utrogestan as usual to make sure you complete the course, but if it is consistently out of sync then perhaps worth trying to sync it by tweaking the cycle as you suggest. Really it is not going to do any harm especially if you are peri and it could be your own cycle kicking in because it means you may be ovulating and therefore producing your own progesterone.
Hurdity x