There could be any number of things. I'll reply in more detail later, but the main thing I would worry about is keeping his conditions spot on, and watching him closely after you feed. After that long with no food, ad not being put into estivation properly, you need to watch and make sure he doesn't start bloating up when he is fed.

Just a sentence or two of soapbox time; When you get an animal whose life you are responsible for, being busy isn't an excuse. I'm in grad school, work two jobs as a TA and RA, and have had a lung infection for the past seven weeks. There have been a lot of days recently when I didn't feel like spending time I didn't have on feeding/misting/watering, but I still did it. I'm trying not to get too mad, but how do you think a dog lover would react if you told them how you almost starved your dog to death and left him outside with no shelter for a month because you were too busy? Neglect is neglect.