For me, mirtazapine knocked me out pretty much from the start so you should hopefully see some relief on the sleep front soon. That sounds like your biggest problem atm making everything else feel so much worse.
Unfortunately it didnt help my mood at all, even on increasing the dose eventually to 45mg (tho that did make me eat anything that wasn't nailed to the floor!)

I stopped it for the side effects and the lack of benefit, but I really missed sleeping 18 hrs a day!
Anyway that's just me so here's hoping that it works for you, and that you get some much-needed rest soon
*Willow*