My heart beats slower than it used to

I was just laying here and i became...conscious of my body. I felt my heart beat, and the blood rush through every single vein. I could feel my blood flowing. Flowing is the wrong word for it, it only moves when my heart does. Pumping is more accurate. I noticed my heart in particular. Its going at a slower rate than it was. Now that i think about it, my heart wasn't racing when i was running this morning. It actually had a rhythm. This is so weird