Hi Po Ts! Another one walking on eggshells here! Exam revision is cranking up and so are the stress levels, so I know what it is like to be waiting for the next "explosion" Teentimestwo ; you have my sympathies! Equally Gandalf46 mine goes through days of being quiet and monollyllabic, followed by mad bursts of energy and loud music! It's not remotely calming to live with! I totally understand that feeling of underlying tension.
Midlifemumofteens that sounds agonising for you. Not many things are worse than watching someone you love and want to do well, struggle with motivation and disengage. It sounds trite, but I have known some teens call a halt on things like this, owing to exam pressure, or other life circumstances, and in retrospect, whilst agony for their parents at the time, they needed that "break" in proceedings to kind of process who they are now and catch up with themselves , and also to simply know that they can have that degree of control. Of the four teens I am thinking of, three came back in to the fold and studied and passed exams and one won a forces apprenticeship. So there is hope! I think some teens really struggle with having things imposed on them, but once they have more responsibility for themselves, after a few false starts, they get the bit between their teeth again. It's this in-between transition bit that is so horribly stressful while we have to stand and watch them suffer and go off down all sorts of rabbit holes. Hope the school nurse proves helpful. 
Welcome to the thread Tarrarra! So sorry about the reasons you are joining us though! That's off the scale stress level stuff!
It's positive that your DS wants to get better though, and remember that progress is rarely linear. Wise words as ever from Billy about unsupportive college. I hope your DS is not feeling too dreadful this morning and that you managed to get some sleep 
And good luck to all Po Ts including Billybagpuss whose teens are "offloading" revision and exam stress on to us parents at the moment. And good luck to the teens themselves of course!
Without wishing to sound over the top and no I haven't taken to early morning gin drinking the more I read the posts on this thread, the more I feel genuinely humbled. So many parents/mothers, ploughing on through relentless agony and unbelievable stress, often while holding down jobs and looking after other DC, who are nonetheless hanging in there for their teens through thick and thin. Us parents may not be perfect and we may have huge wobbles but we are still "present" for our teens in very testing circumstances, and that takes huge love and commitment. It really is an honour being around you lot!
. So things may be hellish, but take the time to give yourselves a pat on the back Po Ts! You deserve it!