Vomiting kitty! Sickness or normal?

Hello all. I have a kitty who is about 8 years old. He's super friendly when you try to pet him but he otherwise keeps to himself. A week ago I went out of town for the night and left him alone with a clean litter box and plenty of food and water. Car rides stress him so much that I hoped it would be easier on him to stay home. When I returned I found diarrhea in multiple places on the floor and 3 spots of foamy vomit.
It has now been a week since the previous occurred. In the past week, each day when I return from work, there is a new hair ball on the floor. (I'd like to add that I have owned him for almost a year and he has never had a hair ball issue) I've started brushing him more regularly with no help. Then lastnight after I fed him, he threw up all his food in the middle of my bedroom. When I was cleaning it up, I moved a box and saw another pile of dried vomit, most likely from the night before (I moved 2 weeks ago to a new place and am still unpacking). He is still very active and friendly and doesn't act as if anything is wrong, except for the vomiting. I was just wondering if anyone else had been through this before with their kitties. I know moving is stressful and I leave early in the AM for work but return early afternoon and play with him everyday. As I'm writing this he is sitting next to me purring and rubbing his face on my arm. I'd love your input.

Well, vomiting is not normal, especially if it is lasting this long, and especially combined with diarrhea.  Yes, stress can cause all kinds of reactions, but I've not normally seen vomiting as one of them.  No change in food along with the move?  And he's still eating and drinking like normal? 

So the diarrhea has completely subsided? 

My cat had a long vomiting spell too and the vet gave me some feline omeprazole for him. We also changed his food to duck and green pea. He stopped vomiting, and the vet says we can try to wean him off the tummy pills soon.

Sophie