We appreciate the sensitive nature of this question and we highly respect your efforts to increase your observance of mitzvot.

The issue of mikveh use by a woman who is married to a non-Jew is complicated, with both halachic and communal ramifications. There are different opinions as to whether hilchot niddah apply to relations with a non-Jew and thus as to whether a woman married to a non-Jew should use the mikveh. Different communities have different policies regarding mikveh use for intermarried women. Since access to the mikveh is a thorny issue, it is up to the local authorities to determine. Therefore, it would be best to discuss this question personally with your local rabbi or mentor, or with the supervisor of the local mikveh.

We wish you much hatzlacha!