What is wrong with my cat....?

My boy cat Leo got pretty fat in the last month or 2...But he is only fat in his belly. Not around his arms and legs and stuff. Is that normal? Also for the last 3 weeks he hassnt been eating very much. like He doesnt eat more then a few pirces a day. But he remains fat and he isnt as playfull anymore. He isnt 1 year old yet This stuff is starting to worrie us but we cant take him to the vet because the last time we took him there he had a cold (which is over but he still sneezes alot) and they gave us some medicine to help him get over it and the bill was like 150$ just for some crap that had almost no effect... oh and i just touched his belly. I didnt feel fat His belly feels a bit firm..or hardish