I finally plucked up the courage / energy to see the doctor today - OK it was the emergency service (thought I had better do it whilst I thought about it not wait for Monday as there was no guarantee I would by then ...) but she was great; had a good talk about how I was feeling, work and how I can manage over the next couple of weeks plus she gave me more pills and will also fax my GP who she says I must see next week to get onto a proper care plan.
At least he will have all the info when I do see him so I will not have to go through that again and it seems he can either sign me off work with something inocuous for week to get back on an even keel (which I think I will go for TBH), or even do a sick note that says I can work but only certain things and preferably not in the office for a bit to avoid the stressors there.
I feel so relieved now I know that those options are there, so thanks to everyone who supported me to motivate myself to go and see someone