When I was pregnant, I was convinced I was allergic to something new in my environment. Almost overnight, I started coughing and sneezing constantly. I felt so stuffed up and even had trouble sleeping. Turns out this is a somewhat normal sign of pregnancy. Pregnancy causes your hormones and blood volume to increase. One of the side effects is that your mucous membranes swell and dry out. When your nasal passages are dry, this signals to your body that it needs moisture, which signals more mucus production. Before you know it, you've used all the tissues in the office because of the constant drip. Many allergy and cold medicines are off limits during pregnancy, so if you're suffering with this constant cold, talk to your doctor. Try easing the dryness with nasal drops and a humidifier. A neti pot is a natural way to clear out some of that built up mucus as well.