Okay, here's the situation:

I've been working out and getting increasingly more tone. Not too long ago, I noticed that my right pectoral muscle has something that seems to be another muscle under it. As I flex my pec, it flexes as well. I tried to look and see if this was a natural muscle that maybe got some definition from improper form when I was first starting working out or something but that doesn't seem to be the case because the other side of my body doesn't have it. Also, i've looked at many bodybuilders and really defined guys to see if any of them have it and they don't. I was just wondering what this could be? I doubt it is part of my pec because it is significantly lower and just generally looks like it's own muscle. When i say "significantly" i mean it doesn't line up the right way to still be my pec. It, like i said, just seems to be another muscle that is located directly under my pec. Any help would be greatly appreciated, thank you!