Minecraft changed skin on its own?

But when I logged in, it changed to this WEIRD robot looking skin. I freaked out because I never changed my skin, and only my dad knows the pass. My dad didn't' change it, he only knows it in case I forget it.
I wasn't offline, I was on Mineplex when this all happened.
I loged into my account on a different computer, and the skin was NOT the weird robot thing. I went to my main comp and it was the robot…
why is dis

Maybe mineplex has a mini game which uses a custom skin
Or
Just Change your password, it might be possible that someone has found it

First try it on a singleplayer world. It is possible that mineplex has a minigame which changes skins. If you skin is still robot you need to change your password. If that didn't help I would send an email to minecraft.

Hope I helped