Breastfeeding

My son is 1yrs old. He will be 2 in July of this year, however I'm trying to slowly get him off my breast. He drinks regular milk any flavor but can't seem to let my breast go. If I refuse to give him my breast he spazzes out and throw tantrums. I will say I love breastfeeding, I've seen a huge difference in him for I also work in a daycare but he's very advanced for his age and very demanding. Any advice is greatly appreciated