he just threw up again and he refuses to eat

He hasn't eaten anything since noon and he's thrown up twice since then and won't touch his water either...
Can heat make them sick to their stomach? It was over 90 degrees today and we tried to keep him inside, but he wanted to be outside... whenever we would move him to the cooler areas of the yard, he would walk back into the sun.
The worst part is that he was doing so much better this morning- ate all of his breakfast and his lunch and he NEVER does
he took a bad fall last week, a couple days before his shot... we should have had him checked out right away and we didn't because he wasn't limping and didn't seem to have any sore spots... we should have mentioned it to the vet, but we didn't because he was acting better... now we're not sure he's been the same since then... I'm so worried we've completely done him wrong

and all he does is love us...