Stuck on helms deep!! lord of the rings the third age.?

ok so i faught with legolas, and i faught with gimli, then i faught with aragorn through thw two battles. Then the battle was done and i was just standing there. no video or anything :( so ive been walking around and fighting for like and hour and a half and everyone keeps saying go protect the front gates. so i go back down and eragorn is there fighting. I walk around trying to get in the fight but nothing happens. ive explored everywhere there is nowhere else to go. im so confused. PLEASE HELP!