Period troubles ?

So when I'm on my period, I get the most crippling cramps, whenever they come I literally have to stop what ever I'm doing and end up doubled over in pain in absolute agony. The pain is sort of all across my lower abdomen and especially painful where my hipbones are and it spreads down the top of my thighs. It's really affecting my life because it affects me at work and I can't really go out because my flow is so heavy (have to change the tampon every 3 hours for the first couple of days). I really want something that will not only help with the cramps but also make my period more manageable ? help?