Good Morning and welcome to the Forum Mommythinks

What you're experiencing is very common with detox and diet change. Take 800mg of magnesium tonight, before bed, to get things moving. Then take 400mg each night to keep things moving. It is an essential nutrient to the body so don't worry about taking it. If the 400mg doesn't work for you, you can continue with the higher dose and even move (ha ha) up to 1200mg if needed. It is a wonderful muscle relaxer and being the colon is a muscle, well, you get the idea.
Keep us posted okay? Let us know how or if it's going. (Sorry couldn't resist the bathroom pun).