Dear OP, unfortunately I know exactly what you're going through. My son took his own life 3 1/2 years ago, aged 15. He was a lot like your son in many ways ... he was kind, caring, compassionate and never once did he show any signs of what he was thinking of doing or of what he was feeling. And to this day we still don't know why our beautiful son decided to kill himself that day, he left no note, he didn't tell anyone of the turmoil he was experiencing.
It's very easy to blame ourselves, to look back and try to pick apart his day to day life. I do constantly wonder why and I honestly think that I will always do that. I've found, through the few odd comments I've received from people, that they are trying to make me feel better 
, that their comments come from a good place, on the whole. My friend that took me aside only a few months ago and informed me that my son was 'in a better place and much happier where he was now' obviously didn't realise or understand that, to a bereaved parent, these comments don't do any good, no matter that her comment came from her heart. Because where is better than with you? With their family? Being loved and cared for. Same goes for those people telling me they know how I feel because their child is now at university/traveling/they don't see them every day. Or the people that say they know how I feel because they lost their grandma/mum/dad/dog/cat!
In the beginning I used to simply nod, now I tell them that they have no idea how I'm feeling and if they can't say anything good then it's better to say nothing at all. But there really isn't anything good that they can say.
I don't know how long it's been for you and I haven't read any of your other threads but you're not alone in your grief. My grief certainly hasn't lessened but it has become something I've learnt to cope with and to live with. I'll never be 'normal' again but I'm ok with that, I wouldn't want to be normal if it meant getting over my sons death.
I'm so very sorry that you are going through this and that you've lost your son, please PM me if you'd like to chat anytime. Best wishes.