Chalak,
You didn't mention if you are drinking enough water. If you have increased your fiber intake with the diet change you will need to increase your water intake. It has been recently recommended to drink half your body weight in ounces of water each day, this can be extremly difficult if like me you are very much overweight.
Have you tried any probiotics? Chances are that you have a yeast overgrowth and constipation is a symptom but it can also be a symptom of yeast die off.
I know this is frustrating but keep up the good work, your diligence will pay off.