Does anyone know what this is?

lolasmit

I have felt the baby kick and punch everywhere up to like the top of my belly button. I know the baby isn't high enough to be by my ribs, which is why I have this question. 

It feels exactly how a kick/punch from the baby feels but it's right under my breasts where my ribs are. Does anyone know what it could be? DH says he thinks it could just be my heart? It doesn't feel like a regular heart beat though? Should I be concerned? Anyone else experience something similar? 

Today it stopped, but yesterday it was on and off throughout the day. 

TIA.