Dark Yellow Discharge, Stomach Ache And Odd Flutter Before Periods

I think I am due to have a period soon, I normally get a stomach ache before I m due. The thing is this time around it feels different, its a dull ache, with the odd flutter and sharp pain . I also have dark yellow discharge and dont feel the need to go to the toilet until I m desperate. I also have to have a check up every 6 months for a smear because 2 years ago I was found to have abnormalities, but since been normal, although Ive not been able to have a smear for over a year as I became pregnant , I had my baby almost 5 months ago now, which was a dry birth.