I'm assuming your doctor or gynecologist ruled out endometriosis. If not, that's a possibility that you need to mention to your doctor.
Let me ask you something; are you taking the medication after the pain begins? As someone who suffers from severe cramps also, I know that it helps if I chart my period so I know when it will come next. Then I begin taking the medicine as often as prescribed a day or two before my period and/or cramps usually begin. Sometimes getting a jump on the pain can make all the difference in the world. Also, heating pads work wonders for me. When away from home you could try using one of those adhesive heat packs. They work pretty good too.

She never mentioned anything about endometriosis. Im trying to ask my mom to make an appointment to go to the doctor so that I can find out what to do about this issue.
I started charting my period when I started birth control.Luckily its almost right on time always now. So I tend to start taking the codine the day it starts (before the cramps start) but this time it came a day earlier than usual..so I couldnt beat it this time. And most of the time I can tell when its going to start hurting so I try to take the codine then.
Heating pads work great for a little while. But not for very long. Im asking my mom when we leave today if we can go buy an adhesive pack to see how well it works.
Im gonna start doing a lot more exercise soon hopefully. That might help a little with my problem.

I hope you find some relief soon.
Here is some information on endometriosis:

Endometriosis is a condition in which tissue (endometrium) that normally lines the uterus (womb) also grows outside of the uterus in places like the ovaries, the bowel and the bladder. This overgrown tissue swells during menstruation and may cause excessive bleeding and intense pelvic pain.
If you have endometriosis, you may be experiencing one or more of the following symptoms:
Severe cramps and menstrual pain
Pain during sexual intercourse
Infertility

I truly hope you don't suffer from this but if you do, it's best that you know about it and treat it as soon as possible.
Take care.

The only thing Im experiencing out of those three (besides infertility...I guess I really wouldnt know about that) is the severe cramps..
I read up on it a bit, and honestly, Im paranoid about it.
I really want to have kids later in life (and my boyfriend does too...we plan to be together for quite a while) and from what I understand, endometriosis can really cause bad things with that...

But people in my family have a bad history with cramps....
Just, apparantly Im more capable of becoming immune to my medicine for it.
Im really thinking its not endometriosis, but being the paranoid person I am, its still going to be in the back of my head until I get to talk to my doctor about it.

Im using an adhesive patch on my stomach right now. It seems to be helping a little. But not enough, sadly. Im still feeling horrid pains in my stomach and I cant seem to get them to go away for anything.
Im looking up more possible ways to help with this. I need to be able to sleep tonight. I dont have room to be sleeping in school tomorrow or anytime during any of my other periods.

Let me know what the doctor says. I'll keep my fingers crossed for a good report and a solution to your problem.

the same thing happened with me, i started in 4th grade and am in 11th grade now as well and i got severe cramps that go into my lower back and legs to where i couldn't walk.
they used to last 3-4 days now they only last for the first day. what i started to do was exercise a lot, make sure you work out your back and abs equally, stretch, and try to eat healthier foods.
sounds crazy but i started to do those things and after like two periods the pain went down and they last a heck of a lot shorter than they used to.
try it out and i hope it works for you as it did for me.
another thing that helps is stretching when you have the cramps, its hard but it will loosen up the muscles.

Im exercising every day..
I dont really have too much room to eat much healthier (I dont eat the healthiest...but in my household I dont have as much of a choice as Id hope)
Im going to the doctor on wednesday so maybe she can tell me some other things I can do.

I went to the doctor yesterday..
Shes sending my to a Gynecologist and Im getting an ultrasound. She thinks its endometriosis.
Im worried that shes putting me on Vicoden though....
A 17 year old on Vicoden cant be good >.<
Oh well...
Next week should be the ultrasound. I guess we'll find out what it is then

I have the same problem i am 21 years old and i started having cramps when i was 13. It seems like they get worse every month slightly but worse, only mine hurts really bad the fist day of my period and somewhat the second day after that it's gone. I went and got a laproscopic procedure and another one i can't remeber the name of it but it was to see if i had endo. The tests were negative i had blood work done and it was normal and i had an ultrasound and everything was fine except a little sist they said was nothing. I still to this day don't know what it is my doctor told me after paying 7000 dollars for this procedure that its normal for some women to have a worse cramping uterus than others but i don't belive it's normal. It's expensive. And i found nothing I hope you have better luck than me cause no one can tell me what it is.