Hey, NewUK, you said you eat "veg". But that doesn't tell me the whole story -- are you vegetarian and eat heaps of GRAINS and a lot of DAIRY? THESE are what could be constipating you. I suffered until I dropped BOTH of them.
Oh, and P.S. Oxy did the same thing to me. I then discovered "MAG 07" and it's much milder yet more thorough! Maybe it'll work for you, too.
That said, since new diet I am winding down the Mag 07 use. I think I have a lot of old stuff to get out still (all due to poor diet, which was supposed to be a good diet -- "healthy whole grains"), but things are moving much better now. My advice is look up caveman diet and stick to this.