Help, uncomfortable pain ??

So I'm on cd13 and been having lower andomin pain for 3 days now. CD 11 I had period like cramps but mild, then on CD 12 I had lower andomin pain and backache, and today Cd 13, I've been having lower abdominal pain all day and still am. I've never had ovulation pains before ever, so I'm kind of confused. What could this be???