What Causes A Delayed Period And Tender Lower Abdomen?

Hi I was supposed to start my cycle on April 18th never got it my periods have been ragular since January and I have a tenderness in my lower tummy area and my boobs don't hurt but the areolas and my nipples hurt I didn't have intercourse during ovulation but I read that change in diet can cause ovulation to be postponed. So I'm a lil confussed on whats going on could I get some answers please