My question involves real estate located in the State of: GA

Hi. I'm getting divorce and I shred a house with my ex husband. I moved to another state, so he stayed in the place and we shared the mortgage and HOA payments. I pay around 1/3 of the total, because that was the proportion of my collaboration to the household during marriage, and, in addition, I'm not living there -that means that I pay rent in another place- so I don't think that is fair. Ex was OK with that.
The house is on the market. I suggested to him to look for a roommate to reduce costs some months ago, and he said that he couldn't find anyone.
Yesterday, through a realtor's answer to one of my ex's email -i was copied in the answer- I found out that he has a roommate, and I didn't know anything! I keep giving him the same amount of money.
I'm mad because he didn't tell anything, and he didin't even ask for authorization, when that property is also mine and I keep making payments.
My question is if I can pay less or pay even nothing at all now that he is receiving money for the roommate. What is my legal responsability over the payment and what is my right over the extra money that he is receiving?
Thanks