What are a fathers financial obligations if child support is already paid regularly?

I currently pay my spouse $1500/month for child support, 1/2 of day care, 1/2 his medical and dental, and 1/2 of his extra curricular activities (boy scouts, karate, etc.) recently she has started to "BILL" me (i.e. she says I owe her) for other stuff like 1/2 of a co-pay for a medical visit, 1/2 the dental bill over what my insurance wouldn't cover. Am I legal responsible to pay for these incidental things also??? I'm not trying to be a dead beat, I just want to make sure she is not trying to take advantage. She works full time and makes a decent wage.
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Yes -- Co-Pays for Dental and Medical over what the Insurance does NOT cover (usually out of plan providers) IS part of your responsibility for Child Support as well. This is a FACT of life -- out of network providers DO charge more for their services -- have you and your ex tried to find in-network providers for the dental and medical?
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