I've noticed that it is getting harder for me to breathe now that I am in my third trimester. I become out of breath simply by laying down or doing simple tasks. Sometime my heart races like I have been running a marathon before bed. Is this normal? It goes as quickly as it comes. I am drinking a lot of fluids and changing positions when I start to feel out of breath. It is just scary at times. I see my doctor this Friday, I just wanted to see if anyone else had this problem?