what could be wrong?

Hi Janelle,
It is not common to have your periods change due to sexual activity. If you are concerned, make an appointment with your physician. Can you keep us updated on what he/she says about your missed period?

Hi Janelle,
Thank you for your question. If you took two pregnancy tests, both of which were negative, you should be safe. Now to answer your question about why your period is late, this could be multiple reasons. One reason is no reason at all. Sometimes we as women miss periods and there is really no good explanation as to why. Other reasons are: stress, different exercise regimes, even hanging around with different women will change your menstrual cycles at times.
If you continue to miss your period and are concerned, consult your physician but most of the time, you may miss one or two and they just come back around as normal. Keep us updated.