Really frustrated this am-down a pound, after doing WW for two days

I'm doing this to stabilize my weight, not lose any more, and to go down a whole pound in that short of time is crazy. I ate 47 points on Monday with no exercise and 39 points yesterday, with approximately 2 point worth of activity (so 37ish points adjusted). I even went to the WW website and looked into signing up, just to get a handle on this, and after doing the fitness evaluation, it said I was too thin and should seek medical advice. I'm still at a healthy bmi, but am down to 19.0. My sister, who's a WW maintainer, thinks I have a parasite
Sorry to vent, I was just really hoping the WW points system would help simplify maintenance and stabilize my weight
