Help a lvl21 lockFollow

I can not seem to figure out what I am doing wrong. I am a lvl 21 blood elf lock. At level 21 I went to the undercity, which I hear was a little late in the game, but I am kind of a noob so i guess I leveled slowly. Anyway, when I got to the undercity, i saw something about a quest to get my succubus, but then solved the quests and dont have further info on the succubus. Additionally, I seem to be in a world now where there aren't too many quests and all the beasts are under my level or over. Perhaps this normal, but in the Ghostlands and previous, the lands were explored as the skills and levels developed. Now I am being sent all over the place, and having a hard time getting thru some of the lands when lvl 30 beasts attack!

Did I somehow end up in the wrong place?

Any help would be much appreciated.

Level 21 and you have been doing Ghostlands. Now you can go to The Barrens, do a few quests, most will be a little low but will give some experience and you can practise different spells, learn to use your succy. Also while in The Barrens head to Camp T and do quests from there the hunting quests you are at the right level for. Tip for The Barrens, turn off general chat or learn to live with immaturity there. You should be able to get to level 23-24 there, also a few quests in Stonetalon Mountains which is next to Barrens and also you can go to Ashenvale and do a few quests. At about 24 as Folsomdog said you can do the quests around Hillsbrad, you could start lower but most mobs are 24-26.

Going to Undercity at 21 isn't really to late, thing to remember that outside Undercity is the Undead starting area and the next zone there is Stillpine which is Undead 12-20 area, you have done the equivalant Bloodelf areas, Eversong and Ghostlands. I think you get the same amount of experience if the quests are green, orange or red, only get less experience if quests are gray, so don't feel that you are to high for an area, if mobs are 5 levels or less lower then you, you still get experience and it helps to learn the game quicker if you aren't fighting mobs that are to tough for you, it may seem to take longer, but I enjoy killing mobs more then constantly running back to my corpse.