Need input please

Ive been having these period like cramps but i dont know why, and just recently its started to cause my lower back to start hurting big time. My sister told me its probably just a poop pain, but i used the restroom and nothing changed, and My aunt said to just drink plenty of water, so i have been drinking as much as i can but so far the cramps still come back as does the back pain. Any ideas what it is? I have a doctors appointment coming up but i was hoping to maybe find out sooner then later incase its something bad.