I'm adhd... so I ALWAYS feel my heart beating. Each and every single beat, all day, every day... and it's interesting because there are different *types* of beats (strengthwise... but different from BP, I'm talking about feeling my heart muscle itself) in addition to different speeds. It was utterly shocking NOT to feel my heart beat, which is what happened on certain types of adhd meds.
I understand non-adhd types have to actually think about their heart beating unless they're running or scared or excited. But I always feel mine. Including the blood flow in and out of it in about 6 inches in most directions. Especially in my inferior vena cava. I only feel my entire vascular system, however, if I've just quit something strenuous. Which is annoying.
When you lay down your BP changes. I can feel that as well, but I don't know about other people.
So I'd 2nd getting it checked out, if it's something new.