I haven't experienced this my self, I have a 13 year old, but as soon as I saw the title of your post I had to answer you. I am so, so, so , so very sorry for your loss.
I know that probably does not help you much but my heart just aches for you, I cannot begin to imagine what that must be like to lose your child in such a horrific and unexpected way.
I'm so sorry that you have to go through this, and I hope that you can find some very much needed help and support here. I also have a history of seizures and my first one resulted in status epilepticus and lasted 45 minutes (which was finally ended due to hospital intervention) so unfortunately my experience is on the other side of the equation, and I was extremely lucky.
These forums, I have found, to be very supportive and I think you will be able to find support and help here. But there must also be places (in real life as well as online) for people who have lost their children, where you could find a more specific understanding as well from people who have also suffered the sudden death of a child. I really, despite all the various traumas in my background, cannot think of anything worse than this.
...I hesitate to say this, because it may be too much for you, but I do a lot of recovery reading sometimes. Melody Beattie, who has written a number of books on recovery and codependence, lost her son at the age of 12, I believe he was on a school trip and died in a skiing accident, also very suddenly. Anyway she has also written at least one but possibly more books on the subject of losing a child. But I recall reading a conversation between herself and a nurse at the time of her son's death, the nurse had also lost her child, and I think she asked about healing (probably if it ever got better), and the nurse told her it took about 10 years. At the time she was understandably overwhelmed by that possibility, but ultimately, she found that was about how long it took her. But you might want to look into her book(s) about what you are going through. She's a really good author and it might help you to know what another person who has gone through it already has found, what it was like for them, what you can expect.
But my understanding is that anything in that range is normal grieving over the loss of a child.
Again, I am so terribly, terribly sorry. And I hope that this doesn't make things any worse for you, if it does, I really apologize.
I hope you will continue to post more here as you go through this process, as hard as it may be.
Hugs if you want them,
Phoenix_Rising