Help! Do I need to intervene!?

[-Flash-]

Good luck.

 

[Pollmadoll]

Not really any progress so far! On day 19 now, I have seen a little bit of rocking, so I have to assume the chick is alive and moving, but can't hear any peeping. There is the slightest crack on the surface of the egg that I noticed (I think) on the beginning of day 18, or end of day 17. It's kind of like a triangle and I thought perhaps the chick was pipping, but theres been nothing else since. I tried to get a photo but it won't show up. It looks like a pip but there's no actual hole, just maybe cracks. Do you think it sounds like a pip? If so, should I worry that the chick is unable to make a hole or zip, or is she just not ready? I'm a little worried but I'm trying not to despair too much since they can be as late as day 20 or even 21.
I'm ready and waiting to intervene, but I also don't want to rush in, incase she's still alive and absorbing the yolk still! This is my first try hatching, so I'm waiting impatiently over here