Assassin's Creed 2, No more Codex pages on map but still need. Stuck on 14 sequence!!?

Hi guys... OK.. On my screen there is Codex Page 23/30 and.... I have gone through all 4 cities but got no codex sign on map. So there r no where no more codex pages to get. I got x16 Decrypted Codex pages. I really don't know what to do. I think the thing I did wrong was going in Codex pages' location n getting them very before sequence 14 n at that time nothing would happen, no codex page in inventory. Guys PLEASE HELP! I really don't know what to do. Been playing so hard this game n reached sequence 14 in just 3 days.... Played vvv much.