I am so sorry for your loss.
You will get through this. Start with a day at a time and if that is too much, an hour at a time, and if it's still too much just make it through the next minute.
My ex-fiance took his life more than 10 years ago. We were not together at the time, and we didn't have a child, which definitely adds much more complexity of emotions. It hurts. Still. And there really are no answers. There was nothing you could have done or said. Let yourself feel everything and grieve. Reach out, especially if you need help caring for your son.
Come here, find a group in real life, whatever it takes to make it through, to help you process, vent, grieve, scream,