Just looking for a bit of advice! I think I am just overthinking it and sorry for it being so long
Started a new job July 2019 and was on 6 months probation, due to end January 2020. In December 2019 I was signed off by my GP for 3 weeks due to low mood and anxiety (delayed bereavement and mental health). After the 3 weeks were over I came down with a really bad flu which resulted in me having an asthma attack so was off for a further 2 weeks to recover. I went back to work when my probation was about to end and they said they would extend it by another 3 months which I totally appreciated and accepted. At the time my workplace were really understanding about it. Said they were there for me if I needed them and not to worry about anything.
Last week I suffered a head injury and was told By my local emergency treatment centre I had some mild concussion and to rest, because I was worried about my probation I went in to work. I told my manager and supervisor what had happened and That I come in because of my probation, I was told not to worry about it and that if I needed to go home then to go but I only did a 5 hour shift so made it till the end. it ended up affecting me really badly, and I went away with my head pounding, feeling sick, dizziness even more than it originally was. The day after was my day off and I spoke to my my GP as I was feeling even worse and was worried but she said it was normal and I really just needed to rest so I took the following day off work (Friday). I went back Monday and everything was fine and then today I received a letter from our HR advisor asking me to go for a extended probationary review meeting next week and it states I can bring a colleague with me if need be. I've never had this before and just wondering if it's anything I need to worry about? My extension isn't due to end till the end of April but it's the 'you can bring a colleague' that's making me wonder its going to be something bad rather than a your probation period is over type thing. It could just be a review like it states to see how things are going but receiving it days after I had a sick day is making me worry. I know I'm probably overthinking it and there's not much I can do till the meeting but just hoping someone has been through similar
Thank you in advance 

