Update:
First, thank you all for helping and supporting me through a very tough time. I'm still in a bad place but a little more stable, i think. I still feel very panicky and anxious and am fighting the urge to flee but I know the only thing I want to escape is myself and running wont help with that.
I saw a GP today - mine is on leave so I had to see someone else. The duty psychiatrist from last week had faxed his letter over to the surgery so the GP read that and was wonderfully sympathetic and said, 'look - you're obviously extememly anxious - you're clutching DP, you're hunched up, your voice is quiet and shakey. We can help by removing one of the stresses so I'll sign you off - how long do you want?' We agreed on this week and next week initially and he said to go back and see my GP then. I made an appointment to see the one I saw today since he listened, was supportive and helpful.
So, after a bad run, I've seen a lovely psychiatirst, a supportive GP and I have 2 weeks at home. Complicated somewhat by my mother coming to visit this weekend (stressful) and DC having surgery next week but at least I don't need to fret about work.
DP has been a big help this week and I have told my sister some of what has happened - not all but at least she knows I'm not in a great place and it's one less person I have to put on an act for. So, things are looking up, I think.