Do you have a counselor or therapist? If ever there was someone who needs the help of a professional to talk to, you're it.
Also, did you ever talk to your ob/gyn about post-partum depression?
In your shoes, I'd also talk to my regular doctor about getting some blood tests done, specifically hormones. If their levels are swinging around, you could get mood swings from that alone (in other words, a physical and not mental cause).
Ask your therapist about talk therapy and about medication (selective serotonin reuptake inhibitors) -- I was on Zoloft for a while and it really helped to even things out.
Please reach out to your medical community, there is help there.
Oh, sweetie. I'm so sorry you are feeling like this. Depression can really do a number on us. There can be triggers with depression (perhaps the pregnancy, hormones, tubal, life with a baby in the house when you thought it was over, trauma of delivery, post partum, etc). Depression doesn't even need a trigger though and just happens.
If you are feeling suicidal, you must ask for help from your doctor. if you think there is any chance you might act on it--- go immediately. The ER, your doctor, call a suicide prevention number. Just reach out. There is no shame in depression. LOTS of people (one in four) suffer from it! And moms have it hard. We are stretched on time, resources and often neglect ourselves. Easy to get overwhelmed.
We're here to support you!
Can you see your doctor? Is your husband supportive?