Why do i get these cramps?

so i am a runner...i am training for a half marathon right nwo taht takes place in october. Right now the distance i should be running is only 8KM...A few weeks ago ( like 3) i started feelings deep abdominal pains and my doctor siad i had severe and deep muscular exhaustion and to take a break..i did but the pains still dont go away. I get them when i run, when i walk fast or go up teh stairs fast...not always but enough to concern me...Its not even my cardio that makes tired or makes me stop its the cramps...i dont even feel like its muscular! its jsut like these piercing stabbing pains..its usually always in the same 3 places on my tummy...Does anyone know what this can be or what i can do? i know it may be hard to understand but anything you know about heaving training for running and how to do it without getting hurt or some negative side effects to training a lot please help! i hate that i cant run anymore it was my favourite things just a few weeks ago :(