Several years ago now a similar thing happened to me. A friend, a girl who was my same age and married for as long as I had been was killed in a car accident. It was...to say it was tragic is an understatement. This out of control truck just took the car her and her husband were riding in off the road and crushed it. He survived and she lingered for a couple of weeks. Her husband said that they had been talking in that moment about starting their family...and then she was gone.
I identified with her so profoundly that I was sick about it....as in sick to my stomach...for weeks...and I would cry randomly. I had the hardest time dealing with it.
I'm wondering if this isn't like a double trauma to you in the sense that it brings your own mortality to the foreground, but it also brings the grief of your mother as well in a time when you are coming up on a milestone anniversary with your mother's death. I think you need to respect this as a terribly difficult emotional time. Losing a parent is really REALLY hard. I lost my own father 12 years ago and as a dear friend put it to me "grief and loss has it's own sense of time". It's just so true. 10 years should mean that it was an entire decade ago but what it means is that you've collected 10 years without your mother...and that's NOT an easy thing to deal with. The death of your classmate has compounded this.
If you need to reach out to someone, try to find a grief counselor or someone who will meet with you for 6 weeks or just a few sessions. It may be very helpful or try to think of a constructive way to honor your classmate and your mother?
My heart goes out to you. I hope your find peace and center soon.