But you say you've had this snake a year haven't you? Have you been live feeding in this way the whole time (leaving in unattended live prey for extended periods of time).

You need to realize that any kind of feeding method is something you have to learn to do properly so your snake is never at risk from your decisions and lack of information. Please use the search feature here and read the many threads on various types of feeding methods (live, frozen/thawd and pre-killed) and how to do each one properly so that it is safe for your snake and humane for it's prey.

There is also a sticky thread on humane euthanisia of live prey so it can be either frozen for later use or offered immediately as a pre-killed prey item.

There's no excuse for leaving a live rat in with a snake like you are doing. If you buy live you need to have planned ahead and have housing for that prey item if the snake refuses to eat that week and you have to hold over a live rat or mouse. A simple small tank with a secure lid, a bit of bedding, a water bottle and a food dish is all that is needed. It's certainly not appropriate to leave it in with your snake and feed it bread.