Hi Casey
I am tempted to say, 'don't worry so much about it...The weight will come back on soon enough' but that would feel like I am belittling your concerns...and I am not.
I was chronically underweight at the time of my k pouch creation (38yrs ago) and wore a size somewhere around 0...now I am a 12 and trying hard to whittle myself down to my comfortable 8...nearly impossible lately.
I am a true believer in listening to your body and its needs, not the dictates of fashion.
Are you feeling better, healthy, stronger? Are you warm enough or chronically cold? Do you sleep well at night? Is your hair falling out in clumps or shiny and strong?
All of the above are indicators of health...not fashion.
If you are cold, achy, your hair falling out (it is Fall so some of it will naturally shed but not in clumps), your skin color sallow then you need help with your nutrition, possibly blood work to help find out what is missing and some supplements.
If you are feeling well and strong, full of optimism and sleep well then your body is probably in balance and the weight will come back naturally in time and maybe it is too soon to rush it.
Forcing yourself to gain weight so soon may disturb a delicate balance and add fat to your abdominal wall that is still healing.
You will put back on the lost weight over the next year, but slowly as your body adapts.
I would go for putting on more muscle mass, doing pilates and some light weights...muscle weighs more than fat and your body will attribute the calories to muscles and bulk up a tiny bit. Useless calories will not help you so aim for proteins and healthy carbs.
Congratulations, enjoy your new pouch...this is a lifetime marathon not a sprint to the finish line...so take your time and enjoy the view.
Sharon