I can't really address irregulaity from personal point of view as I have been regular all my life going no less that twice a day or more. From the time I was a kid I go each morning shortly after getting upthen a couple more times or so the rest of the day. I do the OXY more as a matter of prevention more that anything. I like the ease of doing it and seeing all that black gunk come out. Then I've read glowing report from many. I've tried the BP route but I just don't have the dicipline it takes to do it properly plus you need to do it for 3 or 4 weeks to do some good. I also hated the bloated feeling I got from it.
Have you tried doing probiotics regularly. Perhaps some digestive enzymes and of course diet being the principal thing. I add 4 to 6 oz of kefir to my daily smoofie. Miso also adds beneficial bacterias to the system but the biggest mistake folks make is that they add it at the begining and let boil with the veggies. That destroys the active cultures and enzyme. You must NEVER let Miso boil. You cook all your ingredients and about 15 mins before being done you turn off the heat and then you add it to your soup.Basically all cultured foods stuffs have probiotic benefits.