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.
Both wake and sleep pathways play a role in insomnia. Insomnia can occur when your wake and sleep pathways don't work well together. Science suggests when insomnia occurs, your sleep neurotransmitters may be signaling your brain to sleep, but your wake neurotransmitters may not be turning down like they should.