Oh no, Racjen, you poor thing. I've got no experience of HRT at all but it seems like you need to go back to your GP/specialist for help in getting your dose and combination of treatments exactly right.
I'm so sorry that you feel in despair. It's absolutely awful this anxiety/no hope feeling. I have days when I feel I can't go on and then days when I'm very okay which sums up this hormonal rollercoaster.
I go to work and much as I often don't feel like I can face it, it's good for taking me out of myself.
You say you've been off for 9 months which is long enough to completely get out of the habit of going to work. You also say you've got a phased return. I don't know what you do but is your personnel manager someone you can talk to - if you feel you can, I'd make an appt to see him/her ASAP and be honest about how bad you are still feeling and see if you can delay your return a bit more or start super gently, part time, etc. It may not be appropriate and I've no idea what you do so please ignore that suggestion if it's not suitable.
Hopefully one of the HRT experts on here will come along soon.
In the meantime, try and keep that despair at bay, keep busy, go for a walk, look at trees, call a friend - anything to get through what has started as a terrible day but hopefully will get better x