Congratulations on losing all that weight!
The closer you get to your goal weight, the harder it will be to get those pounds off. If your body mass index is now in the healthy range, maybe it is time to focus on something other than the scale. The scale is so easily fooled by things like water weight that you can't really trust it for small amounts over a short time.
I don't know anyone who hasn't had a week where they have worked really hard and have gained weight.
It sounds like you aren't enjoying food any more. Can you change things up? New foods? I am sure that you can live a fully satisfied life eating 1600 calories a day 95% of the time. Are there some foods that you are missing? Are you feeling deprived?