Does the sensation of a pulse in the sensitive areas on the Day of Arafat, coupled with not remembering to check if anything was discharged, and the presence of secretions that are difficult to distinguish from semen, invalidate the Hajj?

The Hajj is valid, and the questioner should not open the door to Waswasa (obsessive whispering) for herself. The cure for Waswasa is to turn away from it and not pay attention to it. Doubt about the invalidation of ritual purity has no effect, because the certainty of its validity accompanies the original state, which is the persistence of purity, and certainty is not removed by doubt.