I never unlocked the blood oath achievement and I finished the companions questline like 70 hours ago. Anyone know what is going on??

Is there a known glitch?

Not that I'm aware of...

I went through the Companion's quests last because I despise Werewolves, but I got both achievo's, one for joining them and then Glory of the Dead for finishing it just fine with no problems at all...

Sure sounds like a glitch. You can always make a new dude and run him through the first part for the achievement. Blood Oath's the first one iirc? Shouldn't take long.