Happy New Year!!
Choc yes have experience of OH Dr. I found them surprisingly not "on the side of work" but more on the side of the law - i.e. if you have evidence to support what you are saying, that is medical, then they have to accept it. So for example I was able to say when I started anti-depressants and for how long I worked on AD's without it affecting work. OH Dr's tend to think that if there is a medical problem and there is medical treatment for it then they are satisfied. Seeing them is fairly standard I have found - being nervous is normal, if you have advocacy support that is useful perhaps talk to them about what they suggest etc. If you know what you want out of it that helps, going with a clear plan of what you are wanting (even written down a tick list of all the points you want to make is helpful for some people - I need to do that as I forget things).
Remember OH are there to help people into work and stay in work. Sadly bosses try to use OH as a big stick to threaten people, but that can't be their job. And work bosses are not medical people, so use OH to clarify situations. Try to think about what you want from work - eg them to accept that changing your role/redundancy threats/increased workload (or whatever the situation is for you) caused you extra stress and anxiety and it was that work related issue and lack of appropriate support ( change my words for whatever are right for you) that caused you to be signed off, as previous to work changes you worked your hours without significant absence. Then think about what you want from work - a phased return, part-time hours, appropriate job for your skills, redundancy with sick payments, further sick pay to the maximum you are entitled to until your Gp signs you back for work etc etc.
It is normal to be anxious, it is unknown and any type of assessment can feel threatening. If you can go in calm, know what you want out of it and with questions to ask or relevant evidence (even if just your words - eg I was bullied with no evidence but plenty of words to say about it which was listened to) then your place of work have to accept what OH decide. Then if work become difficult OH can become a place of support for you - my OH kept me off work on sick pay longer than I thought I needed, arranged phased return and said if work caused problems to contact OH (work caused massive problems but sadly not ones OH could help with, so I chose to put up with it and cope and find another job with support of OH!!)
Sorry for going on!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Are you still on sick pay? good to know how long it lasts for and what you hope to happen after it runs out (mine was x months full pay, x months half-pay). Even if OH say you are not fit for work, get that report and you can use it to claim ESA etc etc if you need to go down that route.
I have a scary appointment tomorrow, unknown referral and no support etc.