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.
1 In fact, insomnia may be an indicator of depression. Many people will have insomnia during the acute phases of a mental illness.  Physiological related insomnia- Physiological causes span from circadian rhythm disorders (disturbance of the biological clock), sleep-wake imbalance, to a variety of medical conditions.