Sounds like he is going through a deep depression that might need medical help. U have to check if he is routine and work life changed drastically as his relationship with u. Do u have both mutual friends? Did u try make them check on him? Did he even continuing having the same circle of friends or changed it or does he contact anyone at all?
From ur part, u done normal any loving gf would do towards him and it seems that u still care for him deeply but I think if u think that the relationship or the person is worthy u can ask professional advice from a consultant or a therapist and might even demand from him a proper closure or at least for him to try and seek professional help with u. For some these could be invasion of privacy but personally I would try to make sure if that what he really wants, if this feeling was with him since a while or just appeared because of his mother passing, if there is a third party involved?
How long u had been with him?
