Is the oath sworn by a person valid, given the presence of misgivings about his awareness of the oath at the moment he uttered it?

Waswas (obsessive whispering/thoughts) is an ailment that a person afflicted with it must struggle against to overcome by ignoring it. As for the oath, if it was intended, then it is a binding oath (yamin mun'aqidah) that necessitates expiation upon breaking it. However, if it was merely uttering an oath under the influence of waswas without intention, then it is not a binding oath. In case of doubt regarding the issuance of the oath, the default principle is the exoneration of one's responsibility.