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.
In some cases, a medical condition itself causes insomnia, while in other cases, symptoms of the condition cause discomfort that can make it difficult for a person to sleep. Examples of medical conditions that can cause insomnia are: Nasal/sinus allergies.