Cindy,
First off...Welcome! And *hugs*...it sounds like you desperately need one.
I feel for you, because I was in a similar situation. Through high school and into my first year or so of college, I was also on the smaller side. Then because of school and boy problems, I ate horribly and racked on the pounds. I didn't realize how much I had gained (it's hard to notice yourself gaining weight, since you see yourself everyday), until one day I was looking through pictures and saw what I USE to look like! I remember thinking "Oh my goodness, I forgot that those pants use to be HUGE on me...but now I can barely button them!" And from that moment on, I got even MORE depressed...and therefore ate horribly...and gained MORE weight. It was just a downward cycle. Luckily though, I realized I deserved to wake up everyday and feel good about myself. I deserved to look at myself in the mirror and not point out all my flaws. I deserved to feel sexier. I deserved to treat myself better by feeding myself better. I deserved to not be depressed and be happy with myself. So I made a change, and I went on South Beach Diet. And that worked wonders for me. And now I feel a lot better. Not just because I lost weight, but because I'm treating myself and my body with a lot more respect than I use to before.
I hope your reason for wanting to change your lifestyle and eating habits is for yourself, and for no one else. You deserve to enjoy your life and your body, and no one else should be influencing you to do anything that would make you think or do otherwise. Also, I hope you don't feel like you don't belong here because "70 pounds isn't much to lose". 1 pound is a lot to lose if that 1 pound is 1 pound you're uncomfortable with!
I'm not trying to preach South Beach to you, and by no means am I saying what I did was right and what you're doing is wrong. I just want to let you know, there are people out there who can empathize with you, and we're here. And we're willing to listen. And we'll be here for you through this whole ordeal. You can come to us when you're sad from a bad day, or when you need to go shopping for a smaller pair of jeans! We can be a great resource, and you should come to us for anything and everything. And I hope you do!