It's just the pressure from your sneezing. And the extra blood and fluids you have in your circulatory system due to pregnancy can cause you sinuses to be congested.
It's normal. Think of your uterus as a stretched rubber band right now, every time you sneeze or cough is gets a little twang to it and aches for a while. I'm right where you are at 14 weeks and there are times when I'll sneeze and then be in pain for half an hour. And unfortunately pregnancy tends to make you sneeze quite often. If I feel a sneeze coming I tend to curl up a little bit and bend or lift my knees and I find that helps.
i felt tis for the past few weeks, i am also 14 weeks. i get it when i hunker down. iv found doing pelvic floor exercises help. if you feel you are going to sneeze, try sit down if you can or pull the muscles upwards just before you sneeze if tat may help