I'm not such the expert when it comes to eating normally, a combination of anorexia and diabetes makes my list of what I consider "safe" foods that I will eat an extremely limited one. I'm struggling terribly lately, and like you, keep becoming convinced that I've put on weight suddenly halfway through the day.
I totally sympathize because it's so hard! I guess moving away from your "safe" low-calorie foods will be a good place to start. Try a new thing every day.
That's what I would do if I had the strength right now, but I've been in a bit of a bad place lately and find I hold onto anorexia (or it holds onto me) like a 'friend' during hard times and I don't want anyone to take it away from me, weird as that sounds.
Starting to pick up though and when I do, that's when the motivation to change and try new things is at its strongest. I WILL kick anorexia's butt and get my life back. Certainly that's my next step. What did you used to enjoy eating but causes you worry now? Make a little list. Try a little bit when you can. Then try a little more.
An eating disorder is such a complex illness and it can't undo itself overnight. You need strength and perseverance. Every little baby step counts. The more foods you reintroduce, and the less it causes you distress, the more you win. Be strong, remember you need to get the life back that you deserve