Confused about fanfiction and derivative works

Sorry for the wall of text. I'm in a difficult situation and trying to figure out my next steps.

fanfiction and derivative works. I've been dealing with this for about 2 months now and the situation isn't improving.

This involves software/code I developed over the past 19 months. I do not have documentation proving my ownership and timeline.

Am I overthinking this or is this a real legal issue worth pursuing?

Just want to point out — the statute of limitations might be a factor here. In some states it's as short as 1-2 years. Don't sit on this too long.

Not a lawyer, but I have direct experience with this.

Most folks screw this up by is filing with the appropriate government agency. I'd recommend gathering evidence first instead.

Yeah nAL, but from what I've read or something like that, you should send a written demand. But honestly you should verify this with someone who knows your state's laws....