Brain Tumor Surgery

So I have Cushing's Disease which means I have a tumor in my pituitary gland that causes my body to produce insanely high levels of cortisol (stress hormone) that messes with your hormones and causes your body to go into a constant panic mode which results in fat production because the high cortisol/adrenaline rushes make your body think its dying which puts it in survival mode. Normally this causes immense weight gain, however in the last year I've lost 100 lbs. despite the disease advancing. In the last 3 months the symptoms have increased dramatically (bone brittleness, muscular atrophy, joint pain, mental fog, dizziness, panic attacks et al.) and I have surgery scheduled for this Wednesday - ironically, it's on my birthday...which is hysterical because I wished for a surgical date for my birthday.

I'm used to going to the gym 7 days a week but now I won't be able to and I'm terrified about what this means for my weight loss. I normally try and eat within 1200-1400 calories (or half of my exercise calories) with the exception of my birthday week! - so I'm not sure how I can decrease to make up for the lack of exercise and still stick to what is considered a balanced diet. I have no idea what to expect for recovery as the change in hormones will also affect my metabolism. Do I give myself a break and just try and eat healthy or do I obsess over calories that I can't 'fix' with exercise? Honestly, I'm just scared and overwhelmed about dealing with the after-effects of the surgery and terrified that I'm going to gain back what I fought so hard to lose because I don't know how long it will take for me to recover not being able to stick to my tried and true routines. Apparently it can take a year to reverse symptoms doing steroid/hormone replacement therapies and AHHH, I just don't know what to do.