I feel your pain. So sorry
I've always been extremely strict with my eating and slim but after steroids I blew up... And they didn't help. Am now on another drug which puts weight on... So unfair isn't it
But it may be worth you seeing what happens now you're off the meds, without making changes to an already strict diet, as weight may come off naturally, albeit not immediately.
That happened to me in the past, as did gradually get back to natural weight - some was obviously fluid related.
(Trouble is now most of my current medication is supposed to increase appetite as well! And iller I am, the less mobile I am... Luckily (!) I also suffer from nausea!!
)
Good luck.