lilac - "Growth spurts!" They're around 7 or 8 weeks right? If it is any comfort both DD and DS had that around 7-9 weeks. Freaking-out bloody murder screaming. Holding the head up, face beet-red and shaking his fists in mad fury. One night it was 3 hours in a row - fun times. DP wanted to take him to the emergency room. I told him, it is happening only in the evening, before bedtime. If it is something bad, he'll be crying all the time. With DD, it went on for two weeks and you could set a clock to it. Six o'clock and the screaming commenced.
I'd say if the crying is happening at a set time (probably early evening) then I wouldn't worry. If it goes on all day, I'd check with the doctor again.