As someone with occasional Eustachian problems, I can relate to your troubles.
I assume you've tried all the air-moving exercises to equalise the pressure? Tongue pressing against the ridge behind your upper teeth, repeatedly try to swallow (this is the thing that works the best for me, though I've never had a complete blockage; it's called the Frenzel maneuver [1])
Looking at wikipedia [2], there are quite a few variations you might try.
If these don't do anything for you, go see a doctor. This is serious, if it's lasting for a week.