Ok, so i have completed dawnguard on both sides and I've had a go at both werewolf and vampire lord, but i was wondering if there was anymore things to do? I've done the secret paragon rooms in the forgotten vale and I've complete the quest "lost to the ages". But if feel like i still haven't done enough or is it the dlc is really not as "beefy" or full of extra things to do as i thought.

Also I've been having a glitch with the achievements, it displays less gamer score then i have until you actually enter the full list of skyrim achievements. I think the achievements are "the new you" and "awakening" which aren't working. Anyone else having problems like this?

Those achievements were glitched when the dlc first came out. I don't think are still glitched.
Also you can do quests the people ask you to do in the Dawnguard or in the Volkihar side

alrighty i might try out some of those quest and yer my achievements are still glitched weird. hopefully the quests aren't constant dungeon quests.