I don't understand this man

I'm dating this guy who has very limited free time. He works two job has a few kids from a previous marriage that he takes care of and he's starting his own business. So he's really pressed for time, which I understand, BUT sometimes I don't hear from him for days... He says he'll call me back in 15min, but then I dont hear from him until like the next day. So today I left him a message saying this isn't working. it seems like you're just not all that interested in me. and he calls me back really angry telling me I need to check myself before I leave message like that on his phone cuz he's a grown man with responsibilities and if i dont hear from him, I can call him too. Now I'm confused. I really felt like he just wasnt too interested in me, but if that's the case, then why the explosive response? ....

Maybe it just so happens that this whole time while you're waiting for him, he's waiting for you. He sounds very busy. So maybe you just have to accept that you have to be the first one to call