Welcome to Just Answer !
Well, let me explain to you what happened with you. See , since you abrubtly stopped Cymbalta at 30mg without slowly tapering it through 20, 10 mg , you have suffered from SSRI Discontinuation Syndrome ( Withdrawl syndrome) .
Dizziness , irritability, lightheadedness, fainting spells ,sensory disturbances (e.g., paresthesias such as electric shock sensations), anxiety, confusion, headache, lethargy, emotional lability, insomnia, etc are withdrawl symptoms which occur in the discontinuation syndrom of An SSRI like Cymbalta (Duloxetine).
So, my advice to you is that , you go back to 30 mg Cymbalta , instead of present 20 mg , and continue on it for 2 weeks ,and then you start tapering the dose , but this time around , you should taper it through 20 mg , maintaining on it for 1-2 weeks ,and then reducing to 10 mg and then after 1-2 weeks stopping the drug . Well, as for the withdrawl symptoms they are self limiting that is they resolve on their own , but since in your case they are excessive , i suggest you start taking clonazepam , in low dose to alleviate the symptoms along with 30 mg cymbalta , which later on you shall taper.
I WISH YOU RAPID RECOVERY AND GOOD HEALTH.
I hope my answer serves your query according to your satisfaction.