Second stage three sickness panel

To put a long story short, I've just been referred for a second stage three panel due to sickness absence.

I've had a long history of mental health issues, I had a bit of a breakdown 2 years ago due to a variety of factors, both changes at work and issues in my personal life. Last year I had an operation that made my medication unable to be taken and the aftercare sucked, so I wound up off sick for a long stretch which triggered my first stage 3. It resulted in a stage 2 hold and adjustments at work which I think helped generally.

Since then I've had a few sporadic episodes, usually a day or two, the latest however being some pretty intense insomnia after a stint of rapid switches from days to nights, then back, then back to nights again, and the associated anxiety and panic attacks from worrying about it all have had me out for 3 weeks. I've managed to mostly get the insomnia under control, but in that time missed a sickness review meeting and have been informed I'm going back to stage 3, where I'm worried this will be it for me.

I guess I'm mostly looking for any advice people may have. I genuinely like my job and want to keep working, but I'm worried I've let everything down by being like this.