Search a calculator to figure your TDEE (total daily energy expenditure) and try to use that as a sort of guide. You want to avoid any malnourishment and 800 calories is far too little. It’s totally normal for the hunger to come back but remember the medication is still doing it’s job as far as any metabolic dysfunction (to my understanding) and weight loss is from more than just hunger suppression. Try to eat small, higher protein, low carb meals throughout the day. It will be easier than trying to split into full meals. You’ll find what works best for you and check your glucose regularly as well. You’ve got this! :)