Hi, I recovered from anorexia in 2012 and had to gain about 30lbs to get to a healthy weight.
Like you, I was really unsure how I would be affected with the weight gain, and it was a huge source of anxiety for me. After all, I had deprived my body of nutrients for so long, I was scared my body was going to rebel against me and horde weight to the extreme.
The first month of recovery was the hardest. I gained 1 lb every day or two, and the weight jumped on. I was convinced that it was noticeable, but my friends and family all said they couldn't tell - and when I look back at photos, the weight gain was not that noticeable - I just began to look healthier in my face. I have read lots about this, and can conclude that a lot of the weight you put on so fast is water weight, especially if you have been using laxatives or drinking less as a means of weight control. Your body is replenishing its water supply, which leads to a better cognitive and body functioning. Also, your body has been in starvation mode for so long, it's using everything you're putting in to replace your energy stores and your muscles, which is why you crave sugar.
After the first month, my weight gain began to slow down and even out. It gained maybe 0.5lb a week until my body automatically found its 'healthy point' at which the weight gain stopped completely (around BMI 20-21 - but this varies). Lots of people still told me I was skinny, but just a healthy skinny instead of sickly skinny. After three months, I was weight restored so I would use this time frame and accommodate it towards how much weight you have to gain.
I understand how you feel, I was scared I was going to balloon and the weight gain was never going to end, but there is where the strength in recovery comes from, to give up control and trust it to your body to repair the damage and sort itself out, essentially. I wish you the very best of luck in your recovery, don't give up - it's worth it
It's re-gaining control of your life and you'll notice so many benefits - even in photographs, you'll look happier.
x