“Problem with defecating?”

Your body should tell you this naturally in the normal situation. When stool stretches the rectum, then nerve signals are sent to the brain so that you become conscious of the stool that is present and get to a place where you can evacuate it.
There are of course defecation abnormalities that can arise, including simple constipation or loss of rectal sensitivity.

That is an interesting question. Your body should send you a signal with a sense of mild discomfort and pressure in the pelvic area. If you lack that signal you can alter your schedule to enhance that signal. In general, the most physiological time is in the morning after breakfast. If you get up late, skip breakfast, and eat in the car you likely will not have the signal or the opportunity to defecate. Get up early enough to eat a high fiber diet (for instance, I have Familia with walnuts and berries added followed by 2 mugs of hot coffee) and have enough time to wait a few minutes for the signal, defecate, and then shower and dress for work or the rest of your day. If you tend to go infrequently taking Miralax twice daily may help. Once your body gets in this rhythm you might try tapering off the Miralax.

Good question

Listen to your body.