Dr. Told me to NOT gain weight...

Ladies! I just got back from my 20wk appointment and my Dr told me to NOT gain any more weight. But here's the thing.... I'm exactly at my pre-preg weight! I had lost weight during the 1st tri from hyperemisis. (15lb)... I gained that back in the last month but when I was losing I hadn't even been keeping water down. Is it seriously possible to not gain any weight from start to finish of pregnancy??? I feel bad now, should I "diet?" What are your experiences??

I'm 5'5" 220lb and here's my most recent photo just because ;)