Hm the vet said everything was ok with his check up?
Have you thought about an ex-pen?
Kennel-Aire Exercise Pens - Exercise Pens - Crates & Kennels - PetSmart I used this for my yorkie when I got her and it worked out great. I set it up the elongated way. I put plastic runner underneath for accidents and I puet her bed at one end food in the middle and by the door I put her pee pad. That way I could let her out after she used the pad. Pixie is 7 months and fully pad trained and I swear by the ex-pen and the set up. I have a picture of her pen in my albums it is in the album when I first got her.
Does your lil one throw up when it is running around outside the pen?