We already went thru divorce and custody hearings...?

less then 2 months ago. how come i got a letter in the mail telling me that there is another law guardian igned to my son, and that we are scheduled to appear in court at such and such time and date. is my wife trying to pull something. we ended up getting shared custody, both custody and legal. could this have anything to do with child support? why do i have to go to court again after we just went thru this. could she of put another petition in on me? and why? she wanted to have primary custodial (primary residence) but didnt get it. its shared. im nervous, not because i did anything, but because she has already tried to pull so many things, what is it now?