Just as women get PND your OH can get it too. It is an adjustment to their lives also, having to go to work & then coming home to an infant who is unhappy, wanting changing/feeding/sleep & so crying until they're soothed. The thing they forget is that baby knows no other way to tell you something is wrong so they cry until you resolve the problem (which can sometimes take a lot of guesswork going through changing nappy/offering food/burping/rocking to sleep).
At 3mths old baby will be experiencing growth spurts also so will likely be more unsettled. They may well also be starting to teeth becoming very dribbly & irritable, all little milestones but to a tired working OH it is these that can see their patience tested (& mine has commented often these past few weeks how he wishes he had my patience).
Remind him that baby is hard work to look after, that you too have had to be patient with the crying whilst working out what is upsetting LO & how to fix it. Remind him that sometimes all LO may need is a comforting cuddle & shush from Daddy. Also the more angry & upset he gets will only make baby more unhappy (they know when mummy & daddy are unhappy & become unhappy too). Above all else remind him that mummy & baby are greatful for the hard work he does to provide for them & love him lots. It will get easier with time. Best wishes.
