I am sorry to hear you are in so much pain. First, it would be best to tell your doctor you want a colonoscopy. It will rule out anything else that could be causing you pain.
It is my understanding that if nothing else appears then you have IBS. IBS has no physical traits except the C or D.
I have D personally. But still I can relate. Best thing to do until your colonoscopy is to start breaking the cycle. As seen on the first few pages on this site. Or do a search of "Breaking the Cycle" with no time limits and some links will come up.
My symptoms were always there - but it seems that in the past year they just got unbearable. Kinda like how yours got, by your description.
That's about all I can help you with. Keep your chin up, you will see changes and improvements within a few days of starting breaking the cycle. And it will continue to get better and better.
Hopefully others will post for you, as alot of them are very educated in this information and maybe more helpful than me.
Take care and welcome to the boards by the way!
-------------------- Lana_Marie
Proud Mommy to Bentley Taylor
Born May 12, 2004 9lbs, 3oz