Why do I always throw up during my period?

When I get my period I get so nauseous I throw up multiple times a day, one month I threw up like 8 times in two days… I don’t know how to stop it.. I don’t even know what the cause is…

I just want it to end because it keeps me from having a normal life, every month I dread my next period due to the fact I know I will be throwing up.

When my period is near I notice that my gag reflex is worse than usual and sometimes i gag from brushing my teeth.

Maybe it's a gastrointestinal issue but I’m not sure what to tell my doctor..