You should really see a doctor. Your uterus does swell during pregnancy - at the end of the pregnancy the top of your uterus is that bulge starting right under the breasts. However, it does not start to swell until approximately the third month. This is because until then, the baby is so tiny it doesn't need any more room. About the third month, the uterus starts to expand; but, does so very slowly until at the end of the pregnancy, it is larger than the baby.
After birth, it does contract and go back to its regular size.