It sounds like you are a good provider for your little girl. And congradulations, children are like a light shining down on us when it seems the darkest. They are so prescious.
Try to look at the positives, you are a single mother who is successfully taking care of your child. That alone is wonderful, especially with the pain issues. Your pain medicine can make you feel better and even give you a little energy,but(sorry), eventually it could depress you because narcotics do that. Maybe you could ask your doctor for some antidepressants. Explain what you are up against at this time and she should help you. Don't worry about the addiction part, if you didn't need the medication, your doctor wouldn't be prescribing it for you. Are you dealing with fatigue? There are medications for that too.
As for the rage that you went through, that is most likely from holding everything in for so long. I am sorry that your daughter had to see it, but if you explain to her and let her know how important she is to you and try to make her feel safe, I think she will be okay.
Sweetie, you are doing a good job so don't beat yourself up over this. Try to go one day at a time and you will feel better. Take your daughter to the park and swing or go for a walk. You will make it. You are strong, remember that.
And remember that we are all here for you. Keep us posted.
Much love and hugs,