Starting up... Again!

Hi, So this is my third time of starting MFP! The first two times i weighed a little less than what i did when i started this time. My goal is to get back to the weight i felt comfortable and happy at.. I found the last two times i gave up i would stop when i had lost between 7-10 pounds.. not a lot.. i know! So i started last tuesday and have lost 7 pounds already, Just by eating under 1200 calories.. I know that it wont keep doing this though as much as i would love to be able to lose 6-7 pounds a week. I am determined to try and put a 30 minute cardio session into my week as where i work and have a busy social life i find it hard to find time to exercise. But I am determined to change that! I am out of my house in the morning from 8:30am to 9:30 at night! I've started doing 20 sit ups a night so far though.. and every week I will up it by 10 and keep going from there. Anyway if anybody is in the same situation as me, or has had the same situation would love to hear how you are doing with it or how you resolved it! So feel free to add to me :)