I am also experiencing similar pain. I am 19 weeks pregnant and my belly button and the area right around my belly button hurt from time to time. It is sometimes constant but other days doesn't hurt much at all. I have been experiencing this for a couple weeks now.
The immune system is intricately connected to the hormonal system and the brain via messenger molecules, so that emotional stress and factors like insomnia have a great influence on its ability to function properly.
Acute insomnia is often associated with physical or emotional stresses as causative factors. Psychophysiological insomnia, also known as conditioned arousal or learned insomnia, occurs when the individual associates various environmental or lifestyle stimuli with an inability to sleep.