In my VERY humble oppenion, I would not add calories. Seriously, at 5'4" and and a goal weight of 150 unless you do a tremendous amount of physical activity you'll probably have to eat around 1800 calories for life to maintain that weight. Sucks, I know! My Sis is your height and is fairly active. At 140, if she eats more than around 1600 calories a/day she'll gain. She has maintained her weight for a couple of years, and just can't go over that.
I also started out well above 300 pounds and I too dropped a large amount of weight in the first couple months on my plan. Then it slowed WAY down for a while and then picked right back up. I have little cycles like that every couple of months. But when I measure my waist, on those slow periods, the inches are still coming off. Although we would all like to see 4 & 5 pound losses each week, it's just not possible.
Off Topic: If that is a current picture of you, I have to say you carry your weight VERY WELL. I would NEVER guess you at a 300+ woman by that picture...not even 200!
