Multiple causes. There are a number of changes in the body during pregnancy that can affect your comfort and lead to insomnia and restlessness. The increased Progesterone creates a persistent feeling of being short of breath. The increasing hormone levels can lead to nausea. The eventual presistent feeling of your baby moving inside can be disruptive to your ability to rest and relax, as can the enlarging uterus.
Hormones. Hormonal imbalance.