hollo, trust me, your baby is not the only one doing this!! I've had my fair share of bad days/weeks with Nina! What you are describing is what Nina went through at 6 weeks. It was hell for that week, everytime she'd fall asleep she'd wake up 5 minutes later, still be tired, but wouldn't sleep, and was crying constantly. I think she was going through a growth spurt and was just really cranky about it all. And the only time she would settle was if I was holding her.
Does your bub take to the dummy? I know sometimes with Nina it is a godsend! How about comfort feeding? Does she like the pram? If so, maybe taking her for a walk. I've just realised in the last couple of days that Nina loves to go for a walk in her pram, so each afternoon at around 5 we go for a walk and it settles her, and since starting this she hasn't been doing the 'witching hour' thing at night.
One other thing is that she might just be going through a growth spurt?

Good luck to you hun, and let us know how you go.