Weight loss

So the other day I weighed myself and I was 261.5 (don't remember what day it was). I just weighed myself today and I'm below my pre-pregnancy weight at 254. (PPW was 257). I don't eat a lot to begin with (contrary to my weight) but I don't think I should be this low, should I? Should I be eating more? I don't want to freak out but my weight has been going up and down since my last prenatal appointment in August.