You state you have been doing this for two months. Are the existing orders "Temporary orders"? Do you have an attorney already? If so, this is a question best suited for your attorney - please do not be the kind of client that ask everyone you can find for advise so you can go tell your attorney you read or heard a particular thing that is contrary to his/her advice.
Now that I have said that, the answer to your question is: It depends. When was the last order issued and is it Temporary or Final? In Texas, we assume that child custody/visitation orders should not be changed unless there is a reason. That is why your orders state on their face that each of you have possession of the children at all times mutually agreed to in advance (that is how you have been doing your own thing, the court does not care, as long as you both agree). Standard Possession Orders (SPO) take over when there is no agreement. If the orders are temporary, then they are by definition not final, but don't expect the court to give him the extra time by order just because it has been an agreed issue for a couple months. If the SPO you speak of is a final order, then he is blowing smoke unless there is something more than what you are telling here.
Again, if you have an attorney, please speak to him/her. If not, and you live in Collin or Dallas County, please give me a call, I will be happy to talk to you in more detail. Alternatively, you can find more information on my website at: www.planoattorney.net
Roy L. Reeves
Reeves Law Firm, P.C.