Weight gain

I have no idea if this only happens to me but i absolutely HATE it. Im still restricting and only eating my safe foods and my cal limit is still as low as it was at the start of my illness but now i cant seem to lose weight anymore. Like, some days, it goes half a pound or whole pound down, and the next day all that weight comes back and even sometimes adds more and it goes back and forth every.single.day. Like, at the start, i was losing weight fast, as expected ofc, but now it takes me more than a month to lose even a kilo...all that and i still eat as little calories as possible...why? Is this situation expected?

Is anybody else going through this?