Looking for a fiber supplement.....?

I have recently started working out and eating better. I am 5'7 and weigh about 155. I have been doing cardio for 30 minutes a day for 2-3 times a week, and weight machines 2 times a week for about 30 minutes. I am losing weight, but I am not having good bowel movements. I drink probably 7-8 gles of water a day, if not more... eat plenty of fish, and veggies. I was looking for a fiber supplement that would regulate me. I seen something online from GNC that is called Super Colon Cleanse, thinking it was a daily fiber supplement, but it is a regimen that you have to take 4 pills a day for 3 times a day, and not do it for more than 10 days. I have been doing it, and it is working, but what is something that I can take daily to help regulate me... I don't want colon cleansers, just more fiber!!! I eat activa, fiber one cereal, and fiber plus bars too. I cannot find any fiber supplements in the vitamin sections at the grocery, and I DONT want to take laxitives because I am not constipated.