I share 50/50 custody of our son. Who gets to claim him?

He goes back and forth every other week.  Each parent will have him for more time every other year due to Easter/Spring Break  and Christmas holidays.  We have been divorced since 2002.  Last year, we went to court and were granted 50/50 custody with alternating holidays in even and odd years for each of us.  I am disabled with no income and my ex owns his own business.  He told me I couldn't claim him since I have no income.  The subject of who would claim him on their taxes was not addressed at the most recent hearing and my ex wants to be able to continue to claim him since he's self employed. Can I claim him this year since I will have him for more time?  I could use the refund too.