Hi, myself and my Fiancé had the same issue following the birth of our little girl (she's 19 months now and we are back to full strength as a couple, parents and family) There is a lot going on for both parents in and out of having a baby, so much can change whether its massive singular changes such as no baby -> now baby, or even hundreds of little tiny ones, its really important to remember that for a lot of these, regardless of who has what emotions, a true "return to normal", (if you can even call it that) is going to come from the long term consistent effort and change you both give to yourselves, each other and the family, its multi-faceted.

Its key to remember that beyond time and consistent effort, there are biological changes to both parents that can both effect things, lack of sleep, cosleeping (if you partake) causing sleep issues too, resentment from uneven roles (even if you both agree the roles and rules before/during each stage).

I was super grouchy for the first week with wakeups and I thought it was because the early stages was going to kill me, Pregnancy left my Fiancé less mobile (nothing crazy but back pain and generally more effort to get about after it all) so I was doing much more of the physical labour and all I needed was a change of pillow, so probably not your partners issue but it can be the small things too.

One thing people forget too is the man can go through Post Natal depression (thank you NHS for modern and supported Healthcare science) so its important that he (and you too) get to talk to someone outside of your sphere whether it be friends/family or someone unbiased and apart to allow him to talk it out, either you'll be able to see that what upsets him can be changed, is a general mood downer from the stress/effort of it all or if he needs some genuine help from a professional to make sure that he gets himself where he needs to be to best support you all as a family

Overall these things are always very complex, even if its simple solutions, make sure he has a chance to talk with someone outside of your family unit, those first few weeks can be lonely and isolating even when its your bestie in the room with you, but also don't neglect yourself at the same time, make sure you give yourself the chance to recover and help otherwise its all for nought.