SAHM... depression... maybe?

Let me just start by saying I am so incredibly thankful for all that I have. My beautiful son who I wanted so badly, my current pregnancy with my daughter who I also begged for, and my helpful, kind husband who I love dearly. So, why am I so sad all of the time? I wanted to be a stay at home mom and I was so fortunate that my husband was able to find a job to allow that. I wanted these babies. I wanted to take care of them. I want all of this still, but I am really struggling with sadness and anxiety and I'm losing my sense of self... and then on top of that I feel so guilty for feeling this way. I feel overwhelmed and scared and sometimes so frustrated and I want to talk about it with someone but everyone around me has their own issues and hardships and I dont want them to be like "seriously? what do you even have to be upset about?" because I dont know the answer to that myself. I feel so alone despite having so many loved ones around me. I love my family more than anything, so why is it so hard for me to feel happiness and joy? I guess im looking for someone who feels the same things so I dont think I'm just an ungrateful jerk who needs to get over herself? or maybe just so I dont feel so alone with these emotions.