Most Helpful Guy
It's your own fault for listening to your parents and not doing what you want. So you can't blame him for hooking up with other girls because you guys are on a break of your choosing. You could have easily lied to your parents and said you broke up, or you could have actually broken up with him.
If you still want to be with him then stay on the break, but it's unfair to ask him not to hook up with other girls. It was unfair to him when you guys went on break because that's what your parents wanted. He respected your decision, you should be able to respect his as well.