Hi Mosi,
I definitely feel seeing a doctor should be your next step, all the basic blood work will reassure you that you won't have anything truly wrong, and please don't hold back telling your doctor, how scared, depressed, etc you have been. He might be able to help you determine your stress factors that trigger the depression (reason for not being able to sleep at night, thus without a full restful sleep, anybody would be irritable). You are a good mom, you see you need some help, you have made progress joining this group for some online support, and that says for you, " I want to be well", and you can achieve that. Definitely make that appointment as soon as possible. Please keep in touch.
Trish