Weird heartbeat feeling in my throat and chest. What is it?

About a week ago I started feeling what I think is my own heartbeat up in my throat and it feels as though its beating irregularly. I feel a bit more tired than usual but other than that ok. I'm 18w5d pregnant today.

I guess another way to describe it would be this: you know when u listen to music really loud and u can feel the bass in your chest? This is kind of the same feeling, an irregular thumping. I don't feel a diffidence when I put my hand to my cheat to feel it though. I think it's so strange!! Should I be concerned? If anyone could help it would be much appreciated, thank you!