magnesium can help with constipation, so can probiotics.
With excessive gas and constipation, you could be looking at a food intolerance. have you tried keeping a food journal to see if a particular food makes it worse?
Kathy, mother of 3, wife of 1. My new recipe blog: www.kathysrecipebox.wordpress.com (no longer searchable by allergen, but at least it doesn't have a virus!)