You must have skipped a lot of quests. If you didn't skip, coldharbour would have gotten you level 50, I only quest, I don't do dungeons or PvP and it has worked out for two of my characters so far.

I'm not sure what you can do to level since you don't like Cyrodiil and only one dungeon might get you burnt out, hopefully somebody else can give you some help but yeah I just noticed you said you finished all the quests in previous zones which isn't true or else you wouldn't have had this problem.

I think I didn't skip quests.
I have the quests' achievements and went all over the zones looking for skyshards, so I found a bunch of quests as well.

Craft up some gear that gives you bonuses to your exploration XP and go through your list of achievements to find the zones where you might have something. While I don't think you get XP for the achievements, you do get it for doing the things to get them. Other things you could try are Dark Anchors, chests, world bosses, and public dungeons.