My Cat is constantly sick? Please help!?

The other day, (Wednesday night) my cat woke me up vomiting. I woke up after and discovered 7 hairballs on my floor. Last night he vomited Again and ive just come home from school to find sick on the persian rugs and sofas. We took him off the old cat food yesterday. But he did it early this morning and today. Mom's going to get him some cooked chicken from the supermarket. But we're thinking about starving him for a day too, least that might cure his sickness. What's the best alternative and what's wrong with him? We don't have much money and surgery at the vets if needed will cost lots, which we haven't got. Have any of you had a cat like this before?