use benefiber in my decaf coffee 2 heaping tablespoonsful a day does the trick and it is tasteless, dissolves in any liquid had no sugar, 1g of carbs. try it,you'll like it.
Also drinking water helps with constipation.

My bottle of benefiber says there are 4g of carbs in it not 1g. So if taken twice a day, your gettsing 8 g of carbs right there!