Does perjury occur, necessitating an expiation (kaffarah) for an oath or fasting, given that I swore to my husband that I had not spoken to a specific woman since his first trip, intending his second trip, even though I had spoken to her during his first trip?

As long as you swore, intending that you had not spoken to the woman since your husband's second journey, and you were indeed truthful in that, then it appears you have not broken your oath. This is because you were truthful in what you swore about, according to your intention. The intention of the one administering the oath, other than a judge, does not harm you. Therefore, you do not owe an expiation for an oath, nor is it necessary for you to ask your husband about his intention regarding what he uttered. He is not obligated to an expiation, or divorce, or a prohibition. You are obliged to obey your husband in what is good.