25 Year Old Mom Trying to Lose 50-60lbs by July

Hi all. I'm new here. Well, not really new. I have been "dieting" on and off for the past 6 months and just don't stick to anything. I saw some Christmas photos of myself that my mom took and I almost cried with how big I look in them. I decided, I have to change my body. I have two boys who are 4 and 1 and they live with me soley. I'm buying myself the Zumba DVD set this Friday so I will be able to work out at home. Basically, I'm 190 and I want to lose at least 50 pounds by July.
I hope to meet some friends on here who can help keep me motivated. It's really hard for me to stay motivated being so busy with kids, school, and work. I'm often so tired that I just grab whatever I can to eat and it's usually unhealthy.