15pnds over wieght.ive been tryin situps but i cant do over 100 becus it hurts my tailbone.any ideas?im 13 so?

im 13 and am about 15 punds overwieght.ive been tryin situps but that hurts my tailbone and after that i cant walk..ive also tried leg holdup and all sorts of things from magizenes but none seem to work for me?and ive also tryed walkin and joggin..but they didnt work either..im really tryin..ive been for a few months and ive been doin situps and walkin and everythin but its hard because we just moved.so im busy.but ive been finding time for it but it hasnt been workin very good..in the last 2 months ive lost 4 pounds..lol...ive tryin to lose egleast 10 before school starts again.another problem is everyone on my dads side of the family is petit and on my moms they are very um i dont want to be rude but big.ive got alot of my dads side in me...i only have my moms mouth and nose..and feet too.so im petite boddied but im overwieght.mom thinks its because i havent "started" yet ,shes been tlkin to my friends moms and they say after i do i will lose the wight!help!usa_chick_15@hotmail.com