Postpartum depression

So I'm 8 1/2 months postpartum. I want to start out by saying I'm absolutely in love with my baby (I have a really hard time leaving her). 

This past week, I dont feel like myself. I feel very neutral, to be honest I dont really know how I feel (not happy but not sad?). My daughter was laughing with my nephew/sister the other day and dont get me wrong it was cute but I felt like I had to fake feeling happy about it. 

I have not motivation to go anywhere or do anything. I dont want to cook or clean. 

And I'm very irritated with things that wouldn't normally bother me. 

Also, I am having a very difficult time dealing with my feelings towards my mil. Long story short, she annoyed me when I was pregnant. Since baby was born I've seen her on a weekly basis, which is a lot for me (hubby has taken baby for visits a few times and I get 2 weeks away but not often). She has made comments about our parenting (which obviously pisses me off). And i feel very anxious just knowing I have to see her. But she is a good person and means well, I just dont understand why I feel this way towards her. I'm trying to keep my space but it is extremely difficult.

I dont know. Is this postpartum depression? Will these feelings get better on their own?