20 year old 100 pounds to lose!

Im Katie, I am 20 years old and I have been overweight my entire life. Sometimes I just accepted being the chunky girl or the girl out of all my friends that couldnt shop in the junior section, but I have grown sick of it.
I can honestly say though that I want to lose weight so that I am healthier, my family is full of runners and naturally skinny people and sometimes I get really upset when I have to look at pictures and see myself standing next to such beautiful people. I know that I am not healthy and considered obese on a BMI scale, and it makes me sick. I want to be able to wake up every morning and be motivated to eat right and to take a run.
It seems so simple when you think about it, eat vegetables and excersize everyday. but I lack motivation and support among my family.
Ultimately that is why I am on this site. I want to have someone that is in the same boat as I am and who will motivate me and I will motivate them.
I am especially nervous for the school year to start, and for me to find stress with schoolwork and projects and work on top of staying true to a diet or excersize regiment.
I am 5' 4" and I am 237 pounds, my highest weight was 250 pounds and I was going to the drive through everyday, I kicked that habit and saw some awesome results, but now I am stuck, and its now or never to start gaining control.