Owly, do you eat much fruit?
I've found that since I'm back at work and eating more fruit I've had less trouble with constipation.
On a normal day I'll have 200ml orange juice, 2 bananas, an apple, 2 satsuma / clementines and a kiwi. And maybe a plum! It's certainly got things on the go. :-)
I know you go to the gym, but do you walk much? That's useful for helping to stimulate bowel movements.