Changing names on checks

[angelbrite]

I send two checks to my ex every week. One is made out to her(for child support) and the other is made out in the name of the day care provider for our child. i received a receipt from the day care for all the money I have paid through the year, but noticed next to some of the payments that she noted "payment not received directly from..." next to them. i got back the checks that had that notation next to them to prove that I had indeed paid, and found that my ex had crossed out the name of the day care provider on the front of the check and wrote her own name in over it. I also noticed that my ex put my initials (clearly in HER handwriting) next to where she had crossed out the day care provider name and wrote hers.
I am not comfortable with her changing my checks and then forging my initials. What can I do about this?
I am not saying I want her to go to jail...just maybe be told by someone in authority to not do this any more or get a fine?
We both live in New York State.