Over the last six months off an on child support has been sending over payment checks. This has never happen in the past out of all the years that I have been paying c.s. how do I go about finding out what's going on

Call them and ask. Also don't spend the money. Be sure to set it aside in an account until you have this settled.

Yes, sorry I don't want to make it sound too simple, but have you not merely called them, ( or even wrote them and asked them why)

Has there been changes in incomes ? Was there any listed reasons for payment to go down ?