Suggest Treatment For Cramping And Nausea After Taking Ducolax

Hello, I've had to take Dulcolax tablets to have a bowl movement. I have been using it about once a week now, every week for months. The last two times I used it, I got horrble cramping. I was doubled over in pain that came in waves. Last time it was in the morning until I had a bowl movement. Last night I took two tablets instead of three at around 11PM. By 2:30AM I had horrible cramping and nausea, but could not go as it was only a few hours. Why now after over a year of taking this am I having issues? I never had cramps before. Just a bowl movement. I terrified to take this any more, but will never have a bowl movement if I don't!!! Pleas help me? I usually wait until I haven't gone three days, then it's time to take something.