since it is a sudden development u can still try to ask him or any of his close friends you are in touch with about what might be on his mind. maybe things are becoming too much for him to handle and doesnt think of u when it comes to sharing. be open to dialogue or start some written communication between u. small notes for start. show him your appreciation for the things he has done. if he has been considerate to u or ur kids openly thank him so the kids understand too. either he can be depressed and wants to distance from his life and lifestyle or he has other vested interests that has made him feel and think differently for himself. maybe he is having new ideas about his marriage and married life with u . whatever i think u deserve to be spoken to and discuss t openly and try to make possible changes in expectations and effort put into making the marriage more exciting.pls dont try to be passive, its ur life too so ask and discuss patiently esp when in better mood.TC