can't lose the weight

My son is a year and a half and I am a stay at home mom.I don't over eat, but im not very active other than the typical cleaning house and taking care of a toddler. I know i don't drink as much water as I should.I am now 50 pounds overweight and do not like the way I look. my weight will not stay the same it is constantly yo-yoing losing 5 pounds in a week just to gain it right back. I have recently in the last month decided to cut out fast food and soda it has made no difference. I also have started drinking green tea. Spring is here and I can bet on more walking and activity with my son outside.

Does anyone have any suggestions on how to kick this mommy weight?