My heart goes out to you. I'm very sorry that you lost your Mom. In time you will come to peace with your loss.
My father died at 6 am in the morning after I gave up the chair next to his bed to a nurse around 4 am and went to sleep in a waiting room. For a long time I was depressed because I was not there when he died. But, I realized
that what was important were my intentions of wanting to be at his side, just like you. Your intentions were to be at your Mom's side and that is what is most important. Remember that your Mom loved you and her life was a better life because of you and your love for her.