What to do for really bad period cramps?

okk. so at the very beginning of my period i have HORRIBLE cramps. like to where i am screaming and crying..hard core. the only place i can be is in bed, anywhere else and i have a break down. it goes on for about an hour and half. but nothing helps i try to take Motrin but it never really helps. it first started happening at the end of 7th grade and i started my period the summer of 6th grade. my mom is being a ***** about the whole thing. she thinks im am over reacting, but really i am not! and she wont do anything for me. but anyways my cramps KILLS me anything that you think might help that would help THAT WOULD BE GREAT. THANX:)