VERY thin gecko that won't put on weight

I don't know much about geckos. My brother and I both got one when we were about 9. I suspect they were both ill when we got them (they were babies) because we fed them everything the people told us but neither ever got a fat tail or really gained any weight at all. One died after about three years but the other is still alive. I feel awful but she has been without crickets for long periods of time. However, she's been on a pretty regular feeding schedule for a couple months now and hasn't gained any weight. I give her approx. 3-4 crickets and 5 meal worms a day. She poops and drinks regularly and never passes on food. I've read a bit about needing to dust food in calcium and give them vitamins but we were never told to do that. I'd appreciate any suggestions! Also, I'd strongly prefer not to have to take her to a vet. Thanks!

** Gecko is about 8 years old!

Here's a good caresheet that explains a simple leopard gecko setup and all the necessary components:
http://www.onlinegeckos.com/leopard-gecko-careguide-caresheet.html

Please read through that and see what you might be missing. Geckos need food with calcium/vitamin supplements. Also, they need a warm floor surface area around 90 F to digest food properly.

If she has both for an extended period of time and still won't gain weight, she may have parasites. You can ask a vet to perform a fecal test to see if she has parasites, and if so, they can prescribe worming medication.

I'm sorry to hear about the gecko you lost.

It sounds like she is having a failure to thrive, perhaps because of genetics, a disease, parasites, or housing conditions. As suggested above, keeping a worming medication may be very helpful, though it may be expensive (I understand how hard it can be to pay for any vet care for pets. We struggle with that as well). Make sure the enclosure is large, well heated, and provides a dry place to hide and a moist place to hide. Feed gut-loaded crickets (those full of nutrients) and to help fatten your gecko up you could try some waxworms or butterworms. Mealworms are hard to digest and may not be the best option to help a thin gecko. Calcium is also very important, as is vitamin D.

Make sure to clean the cage or at least the droppings up regularly, just in case it is worms or a disease, this will help prevent reinfection. Try to lower the amount of stress that your gecko has to deal with so during handling make sure that your gecko stays warm and comfortable.

I hope some of these suggestions help and she starts gaining weight soon.

Best of luck! : )