Key plot points from The Twilight Saga: The Official Illustrated Guide
- Leah also breaks from the pack and joins Jacob
Leah is irritating; Jacob doesn't want to lead a pack; Leah wants to be free of Sam
- Carlisle and Jacob talk; Carlisle is frustrated because he can't figure out what the fetus wants; Jacob has a thought about blood, and Edward hears the thought and shares it with the others; Bella agrees to give blood a try
It's also highly understandable that Jacob doesn't want to lead a pack. He didn't go off on his own because he wanted to be the Alpha. He was just able to use his birthright to break from the pack in order to take control of the situation and protect Bella. The addition of Seth and Leah forces him to become an Alpha in daily practice. That's not something he was ready for.
The shared concern of Bella is causing Jacob to form a reluctant bond with Carlisle and Edward. They understood the sacrifices he's made to be there and appreciate that. They all want Bella safe more than anything. Jacob isn't letting that stop his less than positive thoughts about the situation which turns out to be the inspiration for Edward's newest idea to help Bella.