My snake's belly scales are damaged

I have an adult male ball python. I got him from an old friend awhile back and do not
know his exact age. I regularly feed him medium rats every two weeks (frozen) but my friend encouraged me to feed him large rats. I fed him a large rat and it took him a very long time to get down and i was afraid it was too much. At first nothing seemed to be different until he had a bad shed and i noticed some of his belly scales were slightly different and there was a brown crust forming in two little areas. I asked my local petco for some advice and they said to just wait and see. His scales seem to look worse and more of the brown crust is forming and my snake hasn't eaten since then or had a proper shed. I switched from his repti bark substrate to newspaper but he hasn't eaten or shed in months! I am very worried and am hoping there is a way to nurse him back without taking him to the vet yet. he doesn't seem to have lost much weight but it's been two and months and i am so worried. He has become less active. If anyone can help give me some advice I can also provide pictures of the scales.

I am no snake expert but i do seem to have luck with disease and bad husbandry(sadly enough).What type of enclosure is he in? It sounds like a burn or scale rot. Sad to say but a trip to the vet will save you alot of stress and should be able to be cleared up. Hope this helps.

Pictures would be exponentially helpful before we try and diagnose anything in terms of the scales. For help posting pictures: http://ball-pythons.net/forums/showt...-Post-Pictures

As far as the rat sizing with meals, it's typically recommended that adult males be fed a single small rat (50-90 grams) per week with the occasional skipped meal being fine. I'm sure the fast is related to the big meal he had.