How could i have fat legs and be thin everywhere else?? its not faiirrrrr?

okay im 51 kgs and 165cm tall...that must be fat because i dont fit into size 10 jeans...i know cos i tried today :(. my goal is to fit into pants before my bday in 2 weeks but i dont think im going to reach that goal because its so close. ive been running for 40 mins every day and eat minimal amounts of food...okay except for that easter egg at night but hello! it makes me happy!. why do i still have fat legs and why cant i fit into pants?? what can i do to fix it?