It isn't at all silly to feel you don't want to go on,it is something many of us have also felt especially when it is all so raw.Right now your only incentive for life is the care of others,and that's probably the best incentive anyone has,eventually you will start to see more but its a long journey that can't be rushed.
Guilt is another one and whatever it is that makes you say it was your fault all of us act in the way we feel is best at the time and we don't have the means to see the future only hindsight and even then no way to know if we had done something differently what the outcome of that would have been either,
The only way through this is slowly a step at a time,you are taking care of your son but you need to take care of yourself too which means being kind to yourself not beating yourself up over something you cannot have forseen .
We will be here as long as you need us to be.I lost my husband and found even just writing helped but this is more than writing because some one will always reach out a hand of friendship and understanding as all of us have lost someone close.