HELP, what's wrong with my dog?

he's constantly throwing uo every 10 minutes... at frist in my room he started making noises so i out him in the kitchen (linoleum flooring is why) and it was a tennisball green but diluted to a yellow.so it was a bright yellow. then about an hour later it picked up and he started every 10 minutes. he's a weird dog... his last tennis ball he ate the fuzz off of and we didn't catch him, and he eats string in his rope. sometimes he gets stuff hes not supposed to get to get our attention for some reason. but when we put him in the kitchen, he sits at the gate and doesn't throw up. is it that hes sick or is he doing it for attention?