I'm so sorry.
It sounds like it would be helpful to talk about your brother's death with someone, because it is making it hard for you to move on.
If you don't have anyone who is close to you and your Mom, it would be helpful to find someone who can work through this with you. If you have a pastor, I know they would be more than willing to be there with and for you. If not, try to find someone, a friend, counselor, or a group of some kind.
If your Mom isn't on Hospice, you can still call them and they can tell you who you can speak with. If she is on Hospice, let them know YOU need help and why. They have resources to help.
I care ...