At the end of a very long tether , need advice and hand holding

[frumpet]

Oldest child is becoming unbearable to live with , I could almost cope with his total lack of care for anything in the house , or anyone else who lives here . I had forgiven his foray into drugs and believed him when he said he had stopped . I encouraged him to speak to the GP about his depression , he is on the waiting list for counselling at the moment .
Yesterday he had a 'fit' at my parents and they took him to hospital on the GPs advice over the phone , all was fine and he came home . Last night I woke to a noise that turned out to be son having a pseudo fit , seen lots of people having them over the years , so am 99.9% sure that this is what it is . Pretty sure he has been taking something ( diazepam seems to be a favourite ) . The noise woke DH and DD , DH went back to bed but DD was very upset and sobbing , managed to reassure her that he was just a bit drunk and it was all fine and she went back to sleep . I eventually got back to sleep at about 3 to be woken again at 5.15 by him wailing because his back hurts , got him some painkillers , he is angry with me because I may have seemed angry when I was dishing out the paracetamol .
I am concerned that he will use his back as an excuse to get more diazepam , so think I might contact GP to flag this and possibly also suggest fits may be pseudo and could they chase the counselling ?
Got to go to work soon , so please don't think I am ignoring anyone offering advice , I am a HCP but not mental health trained so feeling well out of my depth