Faith, i hope you got some sleep, can you leave your DP to deal with DSS for a bit later while you catch up on some sleep?
I don't think i have ever had a conversation with DP about my counselling sessions, apart from to say "its ok" that was what I wanted though, i can't remember if he ever asked. The trouble with my DP is some of the stressors affecting me are affecting him to so he is struggling (but of course being a man he doesn't seek help but internalises it and then can't cope when i have a melt down - i become the reason for his problems - argghhh, but thats us). I found the counselling very personal and didn't want to share it with him, epecially as our relationship was something under discussion.
That doesn't mean that you don't need to and deserve to be able to debrief. It may be that when you find a counsellor that suits you, it will also become you personal thing. Everyone is different.
Its horrible when you can't sleep and i think its always worse when you know you have to get up, its like it is that that is keeping you awake. I remember not sleeping for three days once. It was awful, i was so tired yet as soon as i went to bed my thoughts would be racing. The only thing that snapped me out of that was sleeping tablets, they really helped actually. I didn't have to take them for long (about three days) before it reset my body clock and i was able to sleep.
You sound like a lovely step-mum but your DSS really is your DP's responsibility and he mustn't put that onto you. Yes, you must do things together but he needs to be involved. That is not fair to you or his DS.