I just tried making tea with it to see if it had a reason for living. It smelled great but had virtually no taste. I did steep it a very long time. Not bad, just nothing much for flavor.

I looked up lemon balm, lemon mint, and lemon bergamot. It's none of those. Leaves are much smoother and not hairy.

I tried googling lemon + herb and only found a lot of recipes!

I wonder if it could be lemon thyme, or perhaps lemon savory? Why not spend some time at Google.images, searching for pix of the various herbs you've mentioned, and see which one comes closest to the one you've got.

However, since you've tasted it and weren't all that impressed, why not just get rid of it and replace it with something you know you like - that way at least you'll know what it is!!