Sounds like you want to make your voice(s) into somebody else's in such a way that the listener is fooled. You really can't do this convincingly; it's a waste of your time to try.
There's nothing wrong with layered performances of one voice doing backing. You hear it all the time and usually you don't notice. If you want to draw attention to it, like the early Les Paul multitrack stuff, that's one thing, but you can also just let it fade into the background. They are background vox, right? With appropriate mixing, nobody will notice that it's your voice unless they are specifically listening to the bg vox, and those people won't care because they already like the song enough to listen specifically to the background vocals!
I would put the background vocals through a limiter (each track separately) hitting so that there is always a bit of gain reduction, to make them blend smoothly and under control, and EQ them so that they don't step on the lead. If you are into autotune the bg is where it is worth the humiliation... no better way to draw attention than sour backing vox "harmony"! The 5kHz range is key for articulation and presence in voices; try dialing that down a bit on the background tracks.