Is it obligatory to repeat the circumambulation (Tawaf) after feeling dampness or the discharge of fluid during the two Rak'ahs of Tawaf prayer, while being doubtful if this occurred during the Tawaf itself?

The wetness you observed after completing the circumambulation (tawaf) does not affect its validity, even if it was a drop of urine. This is because the default for every incident is to assess it according to the nearest time, and the nearest time here is when you noticed the wetness. This rule is one of the principles of facilitation and alleviation of hardship. Thus, your tawaf is valid, and you are not required to repeat it. You must relinquish regret after the legal ruling has been clarified.