DH & I both have two children from first marriages and a toddler together. We have my two full time and his two half. Since the beginning of our marriage, if one of his children want to do a sport or activity, him and his ex wife sign them up and I am never consulted or told until a few days before the activity begins. This majorly upsets me and I have spoke to him about it many, many times before. Several times in the past he has told me ex signed them up without his permission. I have caught him lying about this, finding that not to be reality.

He calls me two days ago and tells me his ex signed one of their children up for an activity on a day that we already have multiple things going on with the other children, and also dead during the middle of the one day of the week we spend time together doing something as a couple we enjoy. He says she never asked him, she just did it and what do I want him to do. I broke down in disbelief this happened again after being promised it never would. 
 

We have a toddler together. These decisions affect my schedule and my life. They mean us being separated for many hours on a day we normally spend together. They mean one of us having our toddler alone all day. If it's what we need to do for the kids, I am ok with that, but no discussion with me at all? I have zero say in  anything when it comes to these two kids I am supposed to be helping my partner raise. I am required to, and do, run everything by DH when it comes to my children's activities. 
 

I don't understand how he thinks it is acceptable to do this all of the time, he basically tells me too bad, it's the way it is and there is nothing he can do about it (I don't even believe he didnt give permission, but if that's really the case, I feel like there are certainly steps he could take to address the issue, if it's really an issue with the ex). 
 

I also found out a few months ago he was splitting the cost of activities for his kids from a separate bank account he has behind my back. He has told me from day 1 of our marriage that their divorce agreement was he paid child support until their youngest was school aged (is now), and then at that point they agreed he would either continue the monthly payments but then she would cover everything, or he would not continue the monthly payments and they would split things (she makes a lot more money then him and they have 50/50 custody). If he has to contribute and is required to and lied back then, it is what it is, but admit you lied and move on. He won't do that.
 

I don't trust him at all anymore. Anytime I bring this up to him, how upset it makes me, how he excludes me from everything (all parenting of his two kids is done with his ex wife and/or his mother - in good enough to take care of them at our house but never help with any decision making), and how disrespected I feel, his response is he can't control what she does, he didn't lie, etc. and he always makes every single thing I get upset about that in any way involve his two children (anything, not just related to this issue) it's about me not sacrificing enough for them or me not always doing what is best for them and makes me a feel like a bad person. None of that is what it's about. It's about him disrespecting me and doing things behind my back and breaking my trust. 

I am ready to divorce. We have a million other issues also but this last occurrence of this happening (it's the 5th or 6th time it's happened) after repeadtly talking to him about it, has pushed me over the edge. 
 

I am curious to hear other people's thoughts. I want to make sure I am not overreacting before taking this step and having to split custody of my two year old.