You should vary it depending on how you're beat up. If your legs need to recover you should allow them to recover; if your upper body does then do that. If it's the whole body do that.
Don't be afraid to take rest days if you feel that you need it. Missing one or two workouts especially when they can do you more harm than good (working out while injured can incur greater injuries) is not worth it at all.
Depending on how you're feeling you might want to cut one the days a week and add in a lot of prehab work for everything.