now shiv not confessing his love is due to that guilt and i think its also coz if he tells her she loves her now and then the raaz is revealed ,he thinks gauri will hate and leave him..that will hurt him and the pain will be unbearable and in the process he will hurt her too and that he dont want at any cost..
but if the raaz is revealed and gauri' love for him is the same so then i think it will be the best moment for shiv to confess his love and it will be genuine and no guilt in it..