A woman who experiences uterine bleeding not due to trauma can become niddah even after menopause. The only practical halachic significance of menopause relates to the status of mesuleket damim (a woman who is not expected to menstruate). A menopausal woman who is mesuleket damim is no longer required to observe onot perishah – unless she resumes menstruating three times.

According to some opinions a peri/menopausal woman attains the halachic status of a mesuleket damim if she does not menstruate for at least 90 days after the age of 53. Other opinions set later ages.

However, a younger woman who ceases to menstruate for 90 days needs to observe her onot as soon as she resumes menstruation. Since you are not yet 53, you should still observe your onot perishah. However, since your cycles are consistently longer than 30 days, you only need to observe your interval day and not the yom hachodesh or onah beinonit.

Once your onat perishah passes, you are permitted to be with your husband until the next time you menstruate. However, since you are experiencing irregular cycles, you should use common sense. If you feel you are about to menstruate, you should abstain from intercourse or at least check for bleeding beforehand. You do not need to do an actual bedikah, which would make you niddah if you found blood. Instead, you can wipe externally with toilet paper, not right after urinating. If you find blood, you should abstain until the bleeding either clears up or becomes a period, but you are not considered niddah and do not need to count seven clean days and use the mikveh.