Feeling sad

My boyfriend and I are busy people but I try to make time to talk to him. When we first started dating we talked everyday but twice now he's not responded to my messages for an entire day. He also stopped saying good morning or responding to when I say it.

I work a block away from him and he's welcome to stop by and do hw when he can. I'm feeling a little sad and unwanted but I feel like if I tell him he'll just ask me again why it's a big deal.

I thought about not talking to him for awhile to show him how it feels but I'm not that kind of person.