Question about period pain?

I'm 18 and I get really painful periods, it's getting worse as I get older the pains have caused me to pass out n spend many nights throwing up. I've been to the doctor so many times but they keep saying it's normal I even went to the hospital once and they said the same. I really don't know what to do , I've come on again today n I'm in agony once again.

When would you be concerned about period pain?when does it become abnormal? What should I do? Any advice will be much appreciated !!!