M.,
First, talk with your pediatrician before you try anything else to rule out a medical problem (including gas, GERD, etc.).
My daughter cried from the age of 1 week through 15 weeks. She did not have any stomach problems so it was not a gastroinestinal colic. She simply was overstimulated and energetic and she cried it out every day from about 4 PM to 11 PM. She cried constantly unless she was breastfeeding or catnapping. Nothing worked - the vacuum, the swing, rides in the car, the dryer - you name it, I tried it. I simply resigned myself to the fact that she was medically and physically OK and that she needed to cry every evening. So I just went on with our normal activities. I did keep her in a sling or the Baby Bjorn when she got big enough so she knew I was there for her. I fed her, played with her, read to her, bathed her, and cuddled her all the while she was screaming her head off. I just acted like it was normal. And of course I nevered scheduled anything out of the house during the "witching hours". I also used a cosleeper so she knew I was nearby at night. Cosleeping reduced her screaming from 6-7 hours to about 3-4. She would calm down when she knew we were going to sleep.
It is very difficult to go through but they do outgrow it - usually around 13-15 weeks. So you are halfway there!
Good luck and remember to take some breaks to regain your sanity. Unfortunately my husband refused to help me (he still does - he never does anything with the children except a very occasional play time for 10 minutes a few times a month but that is another problem) and I have no family in the area so I had to deal with it myself. There were times when I thought I would go insane. However I have to say it was an excellent bonding time for me and my daughter since I carried her around with me.
Good luck and if you want to talk, send me an email.
A.