Feeling anxious over sickness meeting at work tomorrow

Hi All

I’ve been called in to see my manager and HR to a meeting tomorrow because of my absence levels and I’m dreading it .
I work for NHS in hospital and have now been off for over 12 weeks due to meniscus tear and being diagnosed with Oesteoarthiritis in both knees after having investigations done over past 3 months .
I rang union up last week to see if they can accompany myself but union rep didn’t give me much confidence as they said I have no protection due to me being on fixed term contract and only working there for less than year .
I’ve been to occ health 3 times and told them I can’t do all the walking round hospital said they’re not allowed to put that in report to my manager .
They keep writing to manager saying I’m unfit for work which I agree with as can’t walk long distances and have been awarded pip and blue badge now for mobility issues .
My manager has been rude and offensive whilst I’ve been off and has made it clear her feelings via email whilst I’ve been absent from work .
The union rep thinks they’ll be finding ways to get rid of me and I’m expecting to be given weeks notice of dismissal tomorrow as stated in my contract of employment .
As if I don’t feel bad enough 😢
I’m still having treatment under inhealth msk for tear and am still having physio and I’ve received cancellation from orthopaedics yesterday and have an appt on 17th Dec to see surgeon to discuss my knee problems .
At moment I don’t feel ready to return physically or emotionally as my job is very stressful !!
My health comes first and I’m not going be bullied into going back sooner to make them happy .
I get impression they don’t believe me and I’m not looking forward to being grilled by them tomorrow .
I will be glad when it’s over as it’s making me stressed thinking about it .😩😩😩