that hours after I poo I need to wipe again?

This mainly depends on the consistency of the fecal matter. If you have fecal matter that is more processed and hard, the body will have an easier time removing all of it when going to the bathroom. If you are one that has the "Peanut Butter" poopies then your body may not be able to get rid of all of it in one sitting. You will find that if you fart a few times or move around a lot, some residual fecal matter will eventually find it's way out the cavity. And to go against what XxBarbie wants, you know when you get an itching/irratating sensation. And yes, I do have this problem also. It's not uncommon, but changing up your diet to include more vegatables (fiber) and some dairy products such as yogurt and cheese will help harden your fecal matter and stop this problem.

Wet wipes don't work, taking a shower won't work. You can't clean what isn't there yet. Another thing that might help is waiting to when you know full well that you have to go and/or staying long enough to make sure you are done.