please help!!!!!

so on the first day of my period I get horrible back pain, diarrhea (like I kid you not, I sit in the bathroom for at least 3 hours as soon as I start) (sorry tmi), awful cramps, and generally can't do anything that day without being in immense pain or wanting to vomit. my whole entire body aches, but it only lasts for a day, and the rest of my cycle I'm totally fine. a friend of mine suggested it could be endometriosis but I'm not quite sure, considering it doesn't last very long. does anybody else have these symptoms to this extent? and if so, how do you get them to stop?