You are guilty of a major sin by thinking of another man while being married. If you had been in genuine love with him, you should have married him. So, you were wrong to marry this man while your heart was with another.

Now there is no use brooding over the past.

If you care about your faith, you ought to forget about the whole affair and try your best to keep your marriage.

To continue to dwell on this is a grave sin.

 

As for the question whether you will be able to be united with him in the hereafter is a question I am not able to answer.

 

Your immediate concern should be to prepare yourself to be worthy of heaven. Heaven is where we will enjoy ultimate bliss, the like of which no mind could ever conceive.

Allah Almighty knows best.