Pure creatine monohydrate, yess even a top quality one like Creapure, CAN cause diarrhea. This happens when the creatine is consumed before it has been fully dissolved in water or solution. if the creatine has not fully dissolved in your water how do expect you body to absorb it when its 70% water. As a result the the creatine sits in your stomach and intestines longer then it would if it was dissolved and pulls excess water into the gut. This excess water being drawn into the gut can cause bloating, cramping and even diarrhea in some.
That doesn't mean creatine monohydrate doesn't work or that you shouldn't take it. I LOVE CREATINe MONO! but you need to let it sit in a warm or room temperature solution for a little while, i.e 20+ mins, before consuming. Or just check to see if your water is fully clear again without any residue on the bottum of the glass/bottle.
The other option would be to get a creatine HCL. Since the creatine molecule is attached to a hydrochloride molecule it has a lower ph and higher solubility rate. making it much faster absorbed into the blood, where it will draw water into the muscle cell instead of the gut like its suppose to.
Goodluck!