Hi Dejibo --
I have been constipated for years! It's the worst. I started taking 2 Magnesium Citrate pills a day and probiotics. Both helped tremendously...I actually started going to the bathroom every day (well almost every day). I was surprised at the difference. For awhile I did probiotics alone but then I had to add magnesium. The only problem is that only one brand of probiotics works for me and it is expensive. But it is so worth it!!! It is called "MegaFlora" made by a company called MegaFood. It has 14 strains of the good bacteria plus 20 Billion per capsule. I take 2 a day.
Here is a link
http://www.megafood.com/products/dai.../megaflora.php
And I use a small bench in front of the toilet to put my feet up on as well. That posture/angle helps. Another thing you can try is massaging an acupuncture point called Large Intestine #4 (called LI4) while you are trying to go. It is between the thumb and first finger--sort of in the web area close to your thumb. If you do press on it/massage while you are trying to have a BM sometimes it helps create peristalsis so things begin to move. Here is a link showing where the point is.
http://www.irufa.com/eng/magnetic/Acupuncture/LI4.jpg
Hope this helps!
Natalie