Strong abdominal pains, knee pain, mucus and yellow substance in stool. What is going on?

It’s been going on a long time now; in fact it’s that long I think it’s normal. I’m not a regular person I usually go once every four or five day's. Some times before I go at least 1 in every 3 I will get very strong abdominal pains, the last six months or so they have got worse. They are now that strong I can not stand it will bring me to my knees and think I'm going to faint or be sick. I will then go to the toilet and my motion is the same as normal just a normal stool formed. Obviously there is a lot but it’s been 4 to 6 days before I have been. A few time there has been mucus some time yellowish some time clear but this is occasionally (in fact every half a dozen times I go) and again very occasionally there has been a deep redness to the poop which I believe to be blood but this has only happened a couple of times in the last couple of years. I have an ok diet and the pains are not always in the morning times they can happen at any time but I would hazard a guess at 70% morning time. I went to AE the other day with what I thought was the start of appendix on my right side and are now booked in for a barium enima. I have the usual pains all around my stomach area which I have never associated with my intestines before I just thought my fallopian tubes where going to explode or rumbling appendix then it all goes away. It’s not very often I get diarrhoea and I do not get rock hard motion how ever sometime I have had to push into my bum cheek as I feel the stool are not inline with the rectum to pass through.
After doing some research into what the Barium Enima is testing for, has made me think there could be other complications!! Is any one else out there got the same symptoms and if you have what was the diagnosis.
I am 40 years of age with 3 kids between 8 and 5. Can you put my mind to rest?