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.
The hormones secreted by the hypothalamus and anterior pituitary that interact with the adrenal cortex are discussed, with implications on sleep disturbances and insomnia. A review of the stages of sleep and sleep architecture is given, and particular attention is paid to the role of cortisol. A dysfunctional HPA and alterations in the rhythm of cortisol production is described as a basis for understanding many cases of insomnia.