Username changed and it wasn't me

So I haven't been on MC for a month or two and when I logged in today my username and skin were different. The password was the same so I was able to log in just fine but I never changed my username and skin. I'm the only one that uses this account so it was none of my siblings.

I had already changed my password but I would like to be able to change my username back soon.

This might be a hacked issue and not a bug I don't know where else to report this