Anyone here gone through open source code in commercial product?

Has anyone dealt with something like this? I'm not sure what my options are.

open source code in commercial product. I've been dealing with this for about 5 months now and the situation isn't improving.

This involves software/code I developed over the past 18 months. I do not have documentation proving my ownership and timeline.

Do I have a strong case? What should my next steps be?

Went through something like this -- ended up getting a lawyer involved which made all the difference.