I feel like I have to go all the time...

I feel you, spengler.  I almost always feel like I have to go (unless I just had D and everything came out).  It annoys me because I will sit on the pot a few times a day thinking something should come out, and it rarely does.
The worst part is that when I do go I feel like it's not all out (unless D).  Sometimes I know there is more there but it just won't come.  It's frustrating.

I don't directly take anything for this. My doc said fiber, blah blah blah... but sometimes I just can't get relief.

No, I guess it's not chronic.... I probably get the feeling every couple days. Usually I only notice it when I eat or get bloated and/or when I go to the bathroom (to pee). It will last for a little while and then I will forget about it.
No, never taken antispasmodics because I don't generally have pain.
Usually I get the feeling in the morning before work. I think it's because I try to go before I leave the house (but that usually doesn't work).
My poo varies from normal to soft to hard and pellet-like. Since I go back and forth from D & C I am hardly ever "normal."