ALot of times if your snake is going into shed they will make a wheezing sounds when they breathe. It's the dead skin getting ready to come off. RI's can be verified pretty easily. If the snake has foaming at the mouth, that is a telltale sign he's got an R.I. Many times they will go off feed as well, but you can't rely on that sign alone as pythons are notorius for going on hunger strikes. Any mucousy discharge from the mouth and vents though are your best indications that you have a problem. If you're that concerned, it would be worth the money to take him to a Herp Vet to be checked out. better to catch an R.I. early thatn take a chance and wait and risk losing your snake altogether.