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 main systems of the human body are the nervous, endocrine respiratory, circulatory, immune, digestive, excretory, skeletal, muscular, and the reproductive systems. They all work together in harmony and unison to keep us alive. The nervous and endocrine systems are what control most of the body. The nervous system includes the brain, spinal, cord and nerves. The endocrine system consists of various hormonal glands such as the pituitary. These two systems interact closely since they both have a part in controlling the body.