I'm sure your beer is fine.
A hydrometer reading is the only true indication of whats going on with your beer. I'd start there.
Re-hydrating a dry yeast will give you more viable yeast cells and a higher cell count, just make sure you do it properly and with attention to sanitation.
Personally, I'm using 150 billion as the cell count I get from a properly stored, re-hydrated, 11.5 gram packet of yeast. This is giving me good, stable and repeatable results.
All that being said, an Belgian under-pitched is a fairly common. The excessive reproduction and weaker cells can produce many of the characteristics you may be looking for in that style of beer.
Good Luck
Brian