What Causes Delayed Periods And Tender And Sore Breasts?

Hi, my name is Jennifer, im 26, epileptic am taking epilim and clonazepam. I started my periods when 14 years old, usually a six week cycle. Past two years now I've had two periods and an episode of slight spotting, definately not pregnant and for two weeks now my breasts have largened and very sore and my nipples feel hot and sore to touch. Please help? My dr suggested going on the pill to regulate period but I want to find out why im not having a period. Im 5 foot 8 inches and weigh 14 Stone. Help please, look forward to reply thankyou, jennifer