I haven't been following this topic, so sorry if my solution has already been suggested
My problem was the opposite - very loose stools. I thought it might be irritable bowel syndrome or diarrhoea. But there was no pain, just a bit of bloating.
After 2 or 3 weeks, I realised it was probably the prunes that I had started having for breakfast. So I stopped eating them three days ago and now I'm OK.
So maybe eating some prunes every day may fix your problem.