Lumps on my cats fat sack (stomach)

I have just recently noticed rather large, flat, rounded lumps around my cats fat sack.They feel firm and fleshy and seem to be under the skin and ontop of the muscle. She has been eating a ton lately, so i dont know if its just fat growth or something serious. She is only nearing 2 years old now, recently she went to the vets and they noticed nothing unusual. Any ideas?

I would not want to guess at this and take her in once more specifically to have it checked. Good luck with your baby!!