If I understand correctly, you're 18 yrs old; is that right? Losing a few pounds wouldn't hurt you, but is unnecessary, since you're not overweight at 109 lbs. 80 lbs, however would be underweight and unhealthy. Perhaps, all you need to do is firm up your muscles, which would require some exercise.
Cutting out sodas and other sweets, chips and snacks would probably be all you need to do, along with a daily brisk walk or some other type of exercise that you enjoy.
No, we won't help you. You're asking us to help you be anorexic. You're not overweight, though you may be out of shape. You want to be so thin you won't be able to get sufficient nutrients to be healthy. Do you have a problem with body image or an eating disorder?
I'd suggest that you first get a counselor to help with body image issues, then try some yoga or tai chi to help tone your muscles, rather than losing weight. That will help with the body image issues, also. It's not healthy to be too thin and it's not attractive.