how much should i eat?

i haven’t had my period in ten months, and i was underweight but not so much. now i am only one kg away from being at a normal bmi. should i eat a lot every day (like 3000 calories) or a little surplus, like eating 2200 cals? because if i eat when i’m hungry i end up not eating enough. also, i’ve gained two kg since i started eating more and i feel my belly a lot bigger, will the weight distribuite better in the future or is just my body that accumulates fat there?