How to know if you have endometriosis?

I know that there needs to be tests done, but how do you know when to push for those tests? I've had my period for 7 years now and they were once very regular from the very beginning. They were painful, sure, but nothing I couldn't handle. Then two years ago they began getting extremely painful. I started having to miss school sometimes because of the cramps and heavy bleeding (sometimes I'd pass out). Then one year ago I started getting these awful migraines with my periods and they started to become irregular. They would start way later and we're becoming longer. My symptoms were getting worse. Then I was put on birth control pills. They've hardly helped. I'm not getting any relief. I can take all the pain killers I want, but nothing helps for more than an hour.

I've thought about, what if I have endometriosis? I've looked up symptoms but I've read that some doctors don't take it seriously at first or just push it off. I'm going to see my doctor in July about my pills since I've had nothing but trouble from them. I want to bring this up, but I'm not sure how since I'm not sure if this is something I'm suffering from. Could any of you ladies please explain your own symptoms and how you were diagnosed so that I could get a clearer idea of whether I'm experiencing endometriosis? Thank you in advance!

***Also, I wasn't sure what group to post this in, so sorry if it's in the wrong one!!***