Fiber Supplements For Diarrhea And Constipation?

ok i have an upset stomach and diherra when i first get up and for a few hours after that then i have dinner and at night im constipated and its the same cycle every day dr just recently told me i have ibs im not sure if i do but thats what he says i read that soluble fiber is good to relieve these symptoms can anyone recommend a good soluble fiber supplement that i could buy at rite aid that will help regulate my system get rid of the diarrhea and the constipation