I've Been Have Extremely Painful Stomach Cramps On My Lower

I've been have extremely painful stomach cramps on my lower belly area before, during, and after eating. I also have the pain while and while not having a bowel movement. My bowel movements usually consists of both diarrhea and constipation at random. I've been having these symptoms for 6 months straight, I've had these pains in the past but not as often or as painfully as I recently have. I've talked to a gastroenterologist about it and has prescribed me (also IBS-C Linzess but didn't help)IBS-D Viberzi to take for twice a day, when I did I didn't feel pain for a while but I wasn't having a bm which eventually caused me to have constipation and more stomach cramps. I've now been told to take for once a day but the cramps aren't going away. I just want to know what it is and how to stop it.