Is this real weight or just water weight?

I'm around 3 weeks into my anorexia recovery, and my weight has gone through the gross water retention thing, now keeps constantly flucuating, e.g. 4lb-8lb a day :S I'm eating around 2000 calories and my metabolism is starting to soaaaar, e.g. hot flushes, fast pulse ect ect but I'm worried this is fat that's aculating on my body? the voice of the e/d tells me I have a huge pot belly now and a chubby face already (history of obesity when I was younger) and I'm really scared to keep eating/increasing calories in case I go back to being 12 stone. I'm a healthy weight for my height right now (5'9, 18 year old girl) so is my weight going to stabilize soon? or keep climbing?!