xposted modifications Needed... Opinions please.

[Modifymenow]

Not sure if this is the right forum to post this so I am posting I'm 3 places!

I have been tracking overnights for over 2 years now and have had my children over 40% of the time for both years.  This is a significant change to the parenting plan agreed upon in the divorce. 
I mentioned to my ex that we need to discuss the fact that I have the kids more than agreed upon and that I want to keep seeing them as much as possible but we need to discuss modifying child support to reflect the changes. 
This did not go over well and now she if denying me the extra nights I was getting to spend with the kids. 
She claims I was just taking them to get a reduction in CS.  This is ridiculous because I want to spend as much time as possible with them, and she has had no problem with that until now, with the mention of money.

My question to all of you is what kind of chance would I have for joint custody, or at least having the parenting plan adjusted to reflect the status quo of extra nights (40+% overnights) thus reducing child support. 

I am afraid a judge will not care and I will end up with needing to adhere to original parenting plan and rarely get tosee my kids.

Thank you.