If you are Ashkenazi, the mikveh attendant you spoke with is correct, and you need to wait a minimum of five days before counting the seven clean days.

Some Sephardi communities, specifically ones who follow the ruling of Rav Ovadia Yosef, wait only a four day minimum. In some communities, this four day minimum is counted from the last time the couple had relations rather from the onset of menses. If you are Sephardi, you should ask your own rabbi for a ruling.

We suggest you read up on this topic in our article about the five day minimum.