postnatal depression in dads!

My husband over the past month or so has days when he wakes up and just feels really low. Our baby boy is nearly 5 months old now. I do absoutley everything, feed him, change him, play with him, bath him, massage him & so on. Don't get me wrong he does the odd nappy change & has playtime but not for long he just passes him back to me. On several occasions I have asked if he would like to bath him, massage him & feed him and he's just said no you do it. I don't mind doing everything as I love it, but I'm just thinking why he doesn't want to be involved much. I'm so scared he's got depression. What can I do. Will giving him more control help at all? Please help as I don't want it to get worse.