I had a very similar thing happen to me last night. I was on my left side, and I could feel the blood really circulating. It concerned me, but I still layed there. Then I started to feel alot of pressure, so I turned onto my back. I'm going to the doctor to get it checked. A year ago, I got a pain in my heart while sleeping on my left side, and went to the er. They said I was ok. I'm a 51 female. Maybe we can stay in touch. my email is doglover894@yahoo.com