Your symptoms sounds very similar to mine (25f). I initially thought it was endo since I used to only have problems around my period - severe pain, cramping, and nausea that often resulted in hospitalization. That went on from age 11-22. It got a lot worse in August 2014 when I started having severe pain after sex, sometimes during. A cramping type pain that would last minutes to hours. Very severe, leaving me curled up just like you describe and often having diarrhea and vomiting. After this pain started it almost immediately began getting worse. Noticeable blood in the Urine with no infection, frequency, and period like cramps almost 24/7. I had a lap done in January 2015 to check for endo, they didn't find anything but a couple fibroids which my doc said shouldn't be causing the issues (I actually cried when I woke up because I was so depressed to wake up to no answers). He sent me to a urologist. I had a cysto and a cysto w/ hydro in February and was diagnosed with IC and put me on elmiron. I've also always have IBS symptoms and had my first colonoscopy at 18. I get very bloated and always have a lot of gas and resulting pain. I often have diarrhea. Around this time, February, I also started getting really bad anal fissures. Like so many the gastro surgeon had trouble counting them all. They were chronic and still haven't completely healed. I had a sphincterotomy in late June to help them heal. No luck. My uro thinks it could be muscle spasms from PFD causing the fissures. My gastro surgeon also diagnosed me with Levitor Ani Syndrome.
Either way, my point is, sometimes there is a lot going on. And I know how much it sucks. Really. People underestimate the pain when you tell them the problems you're having. It can be really depressing sometimes when people don't take you seriously. Find a good doc. And push for as many tests as you can get. If you think it could be endo, push for a lap. Even though they didn't find any with me, I am glad I had it for piece of mind.