mosp, hi.
I know exactly how you feel. Like everythings' not real, like you're not really here and nothings quite real. I had the same quite few years ago. I had depression, but it was due to total and utter exhaustion (ridiculous job, worked 6am-10pm every.single.day.; horrible partner; house move; family death; lots of stress)
I actually ended up in hospital having brain scans etc but there was nothing physically wrong, however the doctors said afterwards my brain took a 'holiday' as i was so tired.
What could I have done differently? I wish I'd signed off sick, I wish I'd allowed myself a rest and a break. Yes, I know it's difficult but somehow you have to. I lost 3 months of my life - I have no memory of that time at all - and I would not wish this on you.
Can you find a way to rest at all? Diazepam is good, are you taking it regularly and not forgetting? Are you remembering to eat, wash etc? - I know it seems pointless as it's not real, but hey, don't take the risk.
You will get better, it takes a little time, a rest and some regular food and medication. If you really really can't cope, can you go to A&E and explain your symptoms?