Sounds like maybe you should have gone longer than 10 days on your cleanse, if you quickly lapsed back into bad eating habits.
The only "harm" of doing it twice in one month is to your metabolism. Remember, when you do the MC, you slow down your metabolism because you've given your digestive tract a rest. You need to give it time to adjust again, to ramp up again, before you shut it down again.
If you don't give it that time, it will be a harder adjustment the next time.