Q.What am I growing?
There is something growing that was here when I moved in. It is some kind of a mint, it smells like spearmint but looks nothing like the pictures on here. I spreads like wild fire. How can I find out what it is? Thank you.

It is estimated that there are over 600 varieties of Mint, both culinary and ornamental.
It very well likely is a Mint plant as they are highly invasive.
Here is a few links for you with information on Mint and how to deal with the issue.
https://www.gardeningknowhow.com/edible/herbs/mint/invasive-mint-how-to-kill-mint-plants.htm
https://www.gardeningknowhow.com/edible/herbs/mint/