A.,
Long story short...we had a VERY VERY colicky baby in 2005 (Jacob). He was horrible and it was very stressful. We decided to have a another baby and I delivered him this August (Ryan). My DH and I were expecting the worst and we signed up for a class "Happiest Baby on the Block" towards the end of my pregnancy.
As it turns out, I delivered Ryan the day before the class, so we couldn't take it until he was about 9 weeks old. We were blessed this time with a very content baby who is comforted very easily. But, we went to the class anyway and it looks like it truly works. I would recommend finding a class in your area and sign up.
As long as you have ruled out medical reasons with your peditrician, this very well could be colic. Colic rears its ugly head in different ways and at different times of the day for babies. Jacob (Mr. Colic) was fine once we were able to get him to go to sleep at night and would sleep for hours at a time and would wake for a feeding ready to play and coo with us in the middle of the night. During the day, he was miserable. Not much soothed him, but here's what I found did work:
Walking around holding him (or in a sling) and bouncing.
Me singing to him (I have a terrible voice, maybe he thought it was funny, lol).
A bath always calmed him down and got him to smile. He STILL loves his baths.
"Shh, shh, shh, shhhhhh". It worked to quiet him down and we were surprised to see that taught in the "Happiest Baby on the Block" class, too.
A pacifier. I was set against them and no WAY was my child going to use one. Yeah, we just got rid of his 2 weeks ago. Lol. He needed it. The sucking soothed him and kept him content.
Good luck.