Please help!! what is wrong with me!!!!!!?

im only 14 and i got my period just a wee while before i turned 12 then it stopped for ages about 8-9 months then i got it back and ever since i got it back my weight has just gone out of control!! iv been eating exactly the same! i gained half a stone in the first few weeks i got it back then i gained another half a stone! so i was up to 10 stone! then i hadnt weighed myself for ages for about 4 months because i was too scared incase i gained more weight! and i just steped on my wii fit 2 day and im 11. 4 stone! what is that about! i really dont understand! i dont feel that fat, clothes are harder to put on! and i dont fit in2 the same clothes as well as i did when i was 9 stone, but iv been dieting for a few weeks and i realli dont understand what this is! do i have some sort of problem! this will really get me down im 14 and im very self concious about my weight! please help!