I too developed this problem and have had it for a good two years now. I know exactly when it started and it was from stress at work.

I tried so many things and even ended up in hospital once with severe pain after many failed er....attempts on the loo...

In the end, I went to my doctor and begged her to sort it out. She had had the same problem and said the only answer for her was:
Recipe:

Dried

prunes
dates
apricots
cinnamon stick

boiled for 15-20 mins with water. Left to cool and eat every morning, if liked with natural yogurt. She said it was guaranteed to work after about 20 mins of eating. She was right! But the thing is it must be eaten every morning (for me anyway) which can get so boring. I've also bought phsyllium husk powder at the Holland and Barratt.

My weakness is bread too and I know I must cut down. Trying to change my diet habits to lots of fresh Thai/Chinese style foods. I love veggies and salads, not too good about eating fresh fruit esp. in winter.

Will try the linseed.

Happy days!