Not new but new issue….please help

I am a many year 12+ user of Reddit., but don’t know where to ask this question. Please help.

About two-three weeks ago I noticed I was posting or under a name I am not familiar with on my profile. I did not create this name. I am ficklefemme but have fuzzy _structure showing up as an alt under me. I gave zero recollection of creating this name. Can anyone\help?