This is exactly what stopped me a few years ago Deb. Wrote out letters to a few people, including ones for my kids to read when they were older which looking back felt really self indulgent. But the thought of them reading them and the impact it would have stopped me at my lowest ebb. When you feel so shit about yourself it's hard to o comprehend how much people really do love you.
I'm so sorry your son didn't have that clarity, I can't imagine how hard that is for you to deal with. You're an absolute gem on this forum and in particular this thread Deb and your son would be proud of the support you give to others