Doubt concerning the number of divorces (talaaq)
Question

                A person divorced his wife but he is not sure of the number of divorces, whether it was two or three. What is the ruling in this case?
Praise be to Allah. 
          If the husband is unsure as to whether he uttered the 
          word of divorce at all, or as to the number of divorces he has uttered, 
          then he should act on the basis of what is certain. So if he is not 
          sure whether he has divorced her or not, the basic principle is that 
          divorce has not taken place, because [in this instance] nikaah (marriage) 
          is something which is certain, and divorce is something concerning which 
          there is uncertainty. One of the basic principles is that certainty 
          cannot be overridden by doubt. If he is uncertain as to whether he has 
          divorced her once or twice, he should assume that he has divorced her 
          once, because this is what is certain.