iMessage from email

My mom recently got an iPhone and when I send her an iMessage it comes from an email that I've never used. my email is firstnamelastname at gmail the messages she is getting from me are coming from firstname.lastname at gmail I've looked in my settings and that email is no where in my phone not for the emails, iMessage or anything else. I don't recall having ever made that address and if I did I've never used it. Oddly I had my boyfriend email me from his phone to the incorrect email address and I received it idk how that's possible. Does the period make no difference in the address?