I'm currently at the quest Alduin's wall, and Esbern is supposed to say something for me to open this door, but hes gone and i can't find him anywhere. I've looked round the camp where the dragon was before we went in the cave and he's not there. I even went back to riverwood to see if he was there but I couldn't find him there. Anyone know how i can sort this out? I don't wanna give up after gettin 33hrs into it.

Just wait 24 hours at the Head/door and he should shows up. At least for me.

The NPCs stop and comment at things like Traps and such to give you hints. If you zipped past them sometimes they still stand there and wait.