Husband is a huge sulker

I’ve been married for 3 years and I’ve got a sweet husband but he loves to sulk. Whenever we have an argument we don’t talk about what happened immediately. He retreats into a box and sulks for weeks. It could be 1 week, 2 weeks or even 3 weeks! I’ve gotten to the point where I just ignore him till he’s ready to speak to me, by the time he speaks to me I’ve even forgotten what our argument was about. I used to initiate conversation and try to get him to speak to me but it just takes so much out of me. So now when he sulks I leave him even it means we don’t speak for 3 weeks. He doesn’t go out much and doesn’t meet with friends even if I encourage him to. He watches movies or sport most of the time especially over weekends. If we do speak we usually get along well and have lots of laughs cause he’s got a good sense of humor.

Any advice?