I had a bit of a scare over the weekend and called in to my doctor's office yesterday and went in for a ultrasound at 10:30am. I have been feeling a ton of pressure in my lower stomach and getting nosebleeds frequently all the sudden (obviously separate incidents). All the nurse heard was twins in our conversation and got me in right away...the one good thing about being considered "high-risk". Turns out both babies and myself are perfectly fine and healthy but they are both head down and getting bigger hence the heavy/pressure feeling. My doctor suggested getting a pregnancy belt which is basically a girdle to hoist my belly up because it is only going to get worse. Oh, the joys of pregnancy I never knew about.
PS- nosebleeds are also common during pregnancy due to the increase blood flow in your body and make your tissues soften. This can cause your blood vessels to constrict, which results in congestion and bloody noses.