PLEASE How can i lose weight?

Ok ever since i turned 8 ive been a bit overweight, right now i think im 5'5 or 5'6, im 15 and i weight 179 pds, how do i lose weight? i do have a bigger upperbody because of my dad, but just.. i dont eat unhealthy food really, i eat a taco that they serve at school, in the morning a lil cream cheese on bread or a bowl of cereal, and my dinners are extremely healthy starting 2-3 months ago, i dont eat fast food from any resturants such as mcdonalds n that shii, but like, idk how to lose weight, please im thinking about going to a dietition or nutritionist or w/e but its $150!!!, so can someone write me a detailed plan on what to do? how to excercide and such? i want to lose 20-30 pounds in the next few months, is it even possible? thanks a ton.