I have really bad pains what should i do :) ?

im 13 and i have been getting side cramps - its really painfull and i dont no what to do - i told my dad that its gone now so i dont put him through any trouble - i occasionallly get it in my back i think it could be period pains but i have had this for about 1 month and still havent started my period :| what shall i do