Doing simple things help. Walking instead of getting a ride to go to to a friend in the neighborhood, etc. Also, if you are involved in school activities that are very active (I do marching band), it helps!
Just a little update, i now only weigh 129lbs. Wooo go me
You are on the right track,.. Just keep the momentum ,and don't get frustrated.
I think runing or swimming is quite good, maybe try doing crunches ? I hope my comment was helpfull! Good luck! 133lbs seems good to me though :)