Tapering off of medications can instigate insomnia and sleep disturbances. If it is caused by withdrawal then a short-term sleep aid might help until your body adjusts, which could take four to eight weeks since discontinuation. I find time release melatonin with l-theanine helpful in going to and staying asleep. Aside from medication I found meditation helpful in going back to sleep; basic breathing exercises. I think the best thing you can do immediately though is to not worry about getting sleep throughout the night. Just stay in bed, meditate, let your mind wander anywhere that isn't worrisome as stressing out is counterproductive.