Scared of the first poop help.

My body does this thing about every other month were it will go to long with out pooping and than I'll get the feeling of flu. I'll get a really upset stomachs than hot and clammy all over. And my temperature will jump. So at this point I'll need to poop. But it's at the point where I physically poop my brains out and puke at the same time. Now I drink a ton of coffee eat fiber rich food coming out my butt. And I habe tried fiber pills. They didn't help. What can I do to avoid this after giving birth?