Constipation is one of the most common symptoms of pregnancy because food digests slower than usual due to increased progesterone manufacturing going on in your body. Your body slows down to let itself to absorb as much nutrients, minerals and vitamins as possible from the food you eat.
Take a very good prenatal vitamin (ask your doctor which one you should take). It is vital to help your body get the nutrients it requires for your developing baby. Drink plenty of water to keep hydrated and help alleviate constipation.
Ask your doctor prior to taking any kind of antacids as some contain aluminum and ought to be avoided. Constipation is one of the symptoms of pregnancy that can last all the way through your pregnancy.