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.
Although it is a sleep disorder on its own, insomnia can also be associated with various other medical conditions that trigger a disturbance in one or more body systems, rhythms or patterns. In other words, sleeplessness can cause or be caused by other mental and physical ailments.