Service tax reversal

Guys.. please solve my query, under service tax we had availed cenvat credit of service tax on under construction units of approx 2 cr, now in gst regime we have received the occupancy certificate. After the occupancy certificate our supply will be exempt but my query is prior to Occupancy certificate we have unsold stock and we had claim the cenvat of unsold stock also so now in gst regime we have to reverse cenvat on proportionate basis of sold & unsold area. Please advise