My girlfriend is a week late, and we're really worried that she's pregnant. She's on the pill, but there was a lapse when she was getting her prescription filled. So there's a possibility she could have gotten pregnant...but she's also really stressed from Uni and whatnot...and I might have given her mono, because the symptoms are just surfacing. So I have no clue if she is or isn't. Does anyone know if getting mono could interfere with your period?