Similar situation?

Okay so for the past year or so my periods every month have gotten heavier & more painful. Painful to the point of me leaving work because it was making my legs shaky & achy. I cramp all throughout the month like I'm gonna start my period. So, I went to the doctor yesterday & she did an examination. She said I had a minor bacterial infection, gave me antibiotics, & said she doubts that'd be causing my periods to be this way but if my period was bad this coming month, she would be looking into endometriosis. She suspects this is the issue at hand. My question is, how do they check you for that? What else could be causing my periods to be so intense? Any advice would be great. Thanks!