If by "on HCG" you mean that so-called "hCG diet" that espouses 500 cal/day with incidental (and bio-UNavailable) oral hCG, then you've already been low-carbing for a while...not to mention starving yourself silly!
Even if all 500 calories came from pure sucrose, that's only 125 grams. And everything's going to feel like indulgence, if that's truly where you're coming from.
A very toned-down version of your current hypervigilance re: total calories may come in useful down the road if you ever stall...but for now, you should eat based on hunger and stop based on satiety, period. Forget calorie counts AND daily scale fluctuations. You want your metabolism to recover and adapt, and "overeating" might actually help with that, even if you gain a few lbs. Then, if you have a lot of excess fat to lose, your hunger should scale back accordingly and weight should start coming off.
Of course, you may also add back some of the muscle you catabolized, which is desirable but will complicate scale interpretation...which again is why you should ignore the scale for now.
6' 2" | Age: 42 | SW: 341 | CW: 198 | GW: 180?
“Life can only be understood backwards, but it must be lived forwards.”
― Søren Kierkegaard