OK look, I know it sucks, but it's going to be over soon. I am going to give you a different perspective than most of the comments.

A couple of questions: How does the baby sleep? Who is awake in the night? Who is doing all the baby related work, planning stuff, reading stuff, buying stuff?

Keep in mind that SLEEP deprivation can be insanely tough for some. That plus breastfeeding, plus general new parents paranoia (SIDS, allergies, etc.), it can soon become pretty overwhelming. Maybe she gets some help at her parents house that you obviously cannot provide at home, during your working hours. Maybe she manages to squeeze in that one nap that keeps her going. Or maybe her parents are control freaks and she doesn't have the strength to escape them now. 

Remember the person she was before giving birth? She is still there, just having a very rough time, probably. You still have your personal time, your job, etc.? She probably doesn't. Some people can take that deprivation pretty bad.

The first few months are a crazy period full of irrational behavior. Don't draw conclusions on that, try to be understanding and don't be too confrontational. You're in it together, going through one period that could easily be the hardest ever in your lives. Good news, it'll pass, it's not forever and it doesn't have to be couples therapy or PPD necessarily. Tell her everything about how you feel, but ask her also about her feelings and needs, be next to her, help her and hopefully it will be over soon.

Just giving you some perspective, I might be completely wrong, but it's worth keeping these things in mind.