Does package yeast inhibit wild fermentation?

If started from packaged yeast, over time, your local wild strains will probably take over. The same is true if you start with a starter from someone else or the dried sourdough starter packages. But, it takes longer even than starting from scratch more than likely for them to slowly replace the current strains.

I would suggest following the link Spagirl gave and some others you can get here and starting again from scratch. Maybe use what you have in the mean time to help stave off the impatience (which I share ;) )

Mine, I was very impatient, so I found that adding some whole rye flour gave the starter a huge boost and got it going much quicker. The theory at least is the bran had a lot of wild yeasts in it and reduced how much the starter had to capture. The somewhat downside was they were not really my local ones, but local will slowly replace those and take over as you starter matures. Long ago though, I made a start as you did, by adding commercial yeast. For months, I was disappointed by the lack of sourness but just before I gave up it turned the corner and the wild strains finally overpowered the domesticated little buggers, so it is possible. I personally though would probably do the restart rather than waiting for that to happen.