Severe stomach pains during / after menses

Hey,

I am 22, female and i have really bad stomach pains, from gastric acid (sometimes) to severe stomach pains. It usualy starts when i am about to have my menses but then i take my IBUPROFEN (ratiofarn) 600 MG to remain stable. Because if i dont, my body starts to change temperature from hot to cold and vice versa, i feel like i am about to pass out and the cramps in my uterus are almost unbearable like i am on the edge to die, then the pain keeps coming and going with maybe 2 min apart. And my stomach begins to hurt serverly and tries to sqeeuze everything out even if i dont have any food. I have really bad stomach pains, and menses pain but if i take IBUPROFEN i usually can function normally on the second or 3rd day. I dont have it every month but every other month. Why do i have bad stomach pains during and sometimes after my menses? The doctor once told me that i had gastric ulcer and a sensitive stomach, he gave me medicine but nothing worked. I am very scared to take my meds on time when my menses is about to start. And last night i spitted some blood, i checked my mouth and and my nose and there was nothing there. I didnt think it was really serious, till it happend again this morning. And the was clear blood when i spit. I think it was from my stomach.

What could it be ?

P.S. i am from holland and the doctors havnt been very helpful they keep saying its nothing but i am sure that something is not right with me.

Thank you,

Milena.