Even if you do nothing mental illness can change over time. Many people with anxiety disorders spontaneously develop sleeping issues. If you have an anxiety disorder or mental illness already, I think the likelihood that is causing your sleep issues is much higher than after effects from 2 weeks of phenibut use 6 months ago. Perhaps the sleeping issues were temporarily caused by phenibut and now are caused by anxiety. Anxiety that it will keep happening or anxiety that you can't sleep. But not actually caused by any structural or chemical change induced by the binge. I would guess this is more likely given the six months and your confirmed anxiety issues.