Isn't it funny how not sleeping can change your own personality? There was a point with my second son when I could feel myself beginning to literally go out of my mind - I'd be driving to drop off my older son for school and forget where I was or where I was going. It can be really scary. (right after the day I was about to check myself into the mental institution to get some sleep, he began to sleep, thank goodness.)
Since your new little one is only a few weeks old, my guess is that he's still got his days and nights reversed. Most babies sleep during the day and are wakeful at night in the womb. You didn't talk about his day schedule - is he napping most of the day?
The other option is that he may be overtired. That happened with my first son, who also had colic. Or maybe his colic was exhaustion. He didn't nap well and he'd get so exhausted that he couldn't get to sleep. Eventually he learned how to nap during the day and then he was less exhausted by night. If he's not napping well during the day, see what you can do to encourage good napping - not right before bedtime, but the after lunch nap. If he naps well in the car, plan drives at that time of day or whatever it takes.
Oh, and find someone to watch him this weekend so you can catch up on your sleep. Even one good night's sleep every couple of weeks seems to help when you have a newborn. Or if possible, have someone else do the late shift while you go to bed at 8 and get a few hours of sleep before he wakes up.
Good luck!