5 yr old getting sick at night.

So my son who's five is getting sick but only at night. He will poop himself and grunt like he is in pain. He had it for two days last week and then we was fine. So I just chalked it up to stomach bug or something. Well this week he got sick Thursday night into Friday and Friday night into Saturday and Saturday night into Sunday he's thrown up each night. The puke is like (tomato sauce) only things I can recall that had tomatoes in it was ketchup on a burger and sauce in pizza. My son is refusing to eat and I think it's getting to the point it's making him sick. His blood sugar this morning read 118 he only weighs 35lbs. He doesn't want to eat the healthy food I put in front of him he wants junk food! He will hold out and starve himself until he gets it. Well now he is sick because of this behavior I am at a loss. I've been told he'll he when he is hungry but that's not the case with him. I'm taking him to urgent care at 8 am when they open to see what a Dr says about it but I just want to know has anyone had this happen before? What was the outcome? I need advice I'm so worried!