Hello there, my 3 year old leopard gecko (F) has in the past few weeks been losing a lot of weight and stopped eating all together. She has become noticeably skinny and is very lethargic. I originally thought she had pinworms, but today when I took her out of her cage to clean I noticed a large purplish lump behind her left hind leg. Could this be a tumor?

P.S. She is housed in a ten gallon aquarium with a heat pad and paper towels. Also i really cannot afford a vet visit at the moment but is their a specific medicine or anything?

Thank you for your input! Please help!!