Weight problems

OK, I know people are tired of hearing fat people complain and blah blah blah! But im not here to complain, and I dont blame anyone else but myself for my weight so lets just get that straigh right now…Ok, well fyi im obese, and I really want to lose weight, I used to never care, but im a junior in high school and im not going to lie that it SUCKS not having a boyfriend, this isnt the main reason why that I want to lose weight but it was the last straw, its really the only thing that is motivating me…the thing is I have no idea where to start! Ok, I DONT eat sweets, theres none in my house, I NEVER drink soda or juice…just water and I drink over the recomended amt. daily, I DONT over eat. The only area I lack is Exercising, I do exercise but its really limited to walking! I need help guys, I know my weight is from genetics, im american indian, with diabetes running in my family, and although im in the all clear for it, I want to make sure I never get it…weight has always been a problem for me and my family, so I really need help, is there any exercises that can really get me losing weight fast, I dont mean to get to my goal FAST because I know it will take time, but that could be noticable in a couple weeks? I want to be thinner by Christmas…please dont tell me stuff I already know, and I dont want some miracle tea or pill, I want to do this the right way, but remember im not just chubby or fat, im obese, I need exercises for that…and yes there is a difference! so please, serious answers only!

BTW My other motivation would be the fact that I have a TWIN sister who got the skinny genes! aint that something?! Shes 5’5’’ and 120 lbs naturally, who eats more than me and is sooo lazy! Ah! its NOT fair…=[ but oh well =p