sounds like your wife is in someway depressed. Not sure whether it is post-natal depression due to the birth of the baby but this can affect women long term and it doesnt necessarily need to be from the outset of birth. Or it could be related to work, or staying at home all day...or something entirely different.
I appreciate this must be very hard and frustrating for you mate!
My advice? Talk to her about going to see your local doctor and she can tell him/her exactly how shes been feeling and they will arrange medication or counselling or something to that effect.
If i was you I would try and find some time to set cook her a nice little dinner at home, get all dressed up for her, buy her some flowers and then tell her you love her and the whole situation is getting you down and talk about going to see the doctor. It will be much better recived in this way i think.
I feel for you tho it must be really hard to go through this. Sorry if my advice stinks i dont have a lot of experience in this im only 20! but hope it helps -x-
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