He probably is a little upset with you as you were gone for a month, some greys react to absences like that, they are trying to let you know you did a bad thing in his eyes by leaving him but it won't last. It kind of sounds like you don't have much time to spend with him and that is not good for him, he needs to know you are there for him some every day. You may be expecting too much from him right now, I think you need to work on your relationship more to earn his trust. Greys are slow to trust and it takes plenty of time and lots of patience on your part as it won't happen overnight. Don't push him for more than he is willing to give, let him make the first more toward more personal interaction with you, talk to him a lot and offer him treats. Another thing to mention, have you changed anything about your appearance lately that may be making him seem as if he doesn't recognize you, with my grey if I put color on my fingernails she doesn't want anything to do with my hands, they notice subtle changes that you may not even be aware of.