Just tell her that you think it's time for an ob-gyn visit, and if she asks you why, tell her that your periods are irregular and you're having bad cramps.
Yes, tell your mom. And have her go with you to see a gyn who is female. Actually have her in the treatment room with you. When you tell your mom, just say it like you did here, ok? And ask her what a gyno doctor does, so you will be prepared for the exam. Good luck -Blu
Yes you should get seen by a Gyno and there is nothing to hide from your mother. It would be good to have her support as bad cramp pain with periods is not normal it could be a sign of Endometriosis.