While we understand your hesitations about immersing on your scheduled night, a timely immersion is encouraged. We hope you can work out the logistics of immersing on the second night of yom tov while still maintaining your privacy. The second seder generally begins later in the evening and you might find time to slip out unnoticed. Further, you should check with the mikveh if they will let you immerse shortly after sunset, as long as you do not see your husband until after nightfall. It would be permissible to use an untruthful excuse (say you are going to shul, or to visit a friend in the neighborhood, etc.) in these circumstances. Alternatively, it is permissible to tell another woman where you are going if necessary.

Despite the fact that you are on the pill, and thus you are not actually delaying the mitzvah of pru u’rvu by postponing your immersion, there still remains the mitzvah of onah that should not be pushed off unnecessarily.

If your attempts at working out the logistics do not succeed, and you still feel that you would really be uncomfortable immersing seder night, you and your husband may agree to your delaying immersion until Motzai Shabbat.

In the future, as long as you are on the pill, you can choose to manipulate your cycle to avoid awkward mikveh nights. In this case, you could have taken two or three extra active pills (from a new pack) to delay your period for a few days, thus pushing off mikveh night until chol hamo’ed.