Are you eating enough at meals? Are you eating enough fat? Are you eating by the clock?
We advise eating to satiety; i.e., not eating till hungry and stopping eating when satisfied. This works well for most people. If you feel the need to snack between meals, eat a fatty snack, and then eat a bit more at the next meal. The body will eventually sorty itself out. If you’re pre-menopausal, note that your cycle is going to affect your appetite. Nothing wrong with just riding with it.
The advantage to eating to satiety is that it eliminates the need to calculate macros (other than to keep carbohydrate under the limit) or calories. Since a ketogenic diet is very low in carbohydrate and moderate in protein, that leaves only fat as a source of calories, which feels counter-intuitive to people born since the dietary guidelines were first promulgated. But fat actually has a negligible effect on your insulin secretion, so it is actually the safest source of energy for our bodies. In a low-carbohydrate setting, it’s not going to get trapped in our fat tissue, and it will satisfy our appetite enough for our body to use some of its excess stored fat for fuel.
I think the real answer to your question is that your body hasn’t completely sorted itself out yet. Give it plenty of resources (food), and it soon will. If you find you must snack, make sure that you munch on something low-carb and high fat.
But you must be doing something right already, because losing 20 lbs. of fat in two months is pretty impressive.
P.S.—Don’t try to fast until it starts happening naturally. For now, eat!