Do you have the stomach pains at any other times apart from your periods? If so, then it is possible that you have something such as fibroids or cysts and a USS can reveal this.
You do not have to live with the pain either. There are lots of other natural alternatives that work and it is not just a question of taking OTC meds to help. There is more to life than pill popping in this way.
Firstly, have you tried putting heat pads or a hot bottle on your belly? If not, then this can really help as the heat helps your muscles to relax and if they relax, the cramps will go. Sometimes, stretching out your belly muscle can help to ease the pain too. Lie on the floor and stretch your belly gently by doing mini situps. Doing this can help stretch the muscles and help the pain too.
Also, homeopathic remedies are extremely good for period pain. You need to find the right remedy though. Severe cramping pain normally responds to MAG PHOS and you can get these remedies from a healthfood store.
Lastly, another good form of treatment is acupuncture. This works extremely well for PMS as well as period problems generally. If the other things do not work, then I would suggest that you try this.