why do I feel like this?

I had my son on halloween at 34 weeks. He had to stay in the hospital for 6 days and then we got to bring him home, he has been doing absolutely amazing.
But my husband had to start back to work on Monday (yesterday) and I've been falling more and more into such a sad trap I can't get out of. I cry so much throughout the day, I have thoughts like "maybe I got pregnant too soon" or "I wish it was just my husband and I again" and I hate these thoughts because my son is my world. I don't have much of an appetite, it's currently 4 pm and I haven't ate a single bite of anything at all, and I'm still not hungry. I don't sleep at all, my body is drained. I'm also home alone all day every single day because my husband is at work and I notice that I get way more sad being alone all day, I'm just so so sad. I feel sad because I had him so early (out of my control but still) I'm sad because when I try and pump for him I can barely get anything at all. 
When will this get easier?