Am I obligated to offer expiation every time I do something I swore to abandon and offered expiation for my oath, given that I don't recall my intention at the time of the oath concerning repetition?

You must abandon this sin and repent of it. You are only required to offer a single expiation for a broken oath (kaffarat yamin), and your oath has been absolved by that expiation. The expiation is not repeated with the repetition of the action because you did not utter a phrase indicating repetition, and the default is not to intend repetition as long as you are not certain that you intended repetition.