Constipation is incredibly common during pregnancy; in the 19th century, some people called pregnancy the Disease of Constipation. The good news is that all the remedies and treatments you might normally use for constipation are still safe during pregnancy. You should start by increasing your water and fiber intake. Many women will add daily use of MiraLAX or a generic equivalent to their diet. This is a gentle agent that is non-stimulating and safe to use during pregnancy. If it has been a few days since your last bowel movement, you may need to stimulate a bowel movement from below. Try using a suppository (e.g., glycerin or Dulcolax), and if this doesn’t work you can repeat it in two hours.
If these over-the-counter remedies are not helpful, talk to your doctor.