Yeah,that's the thing with lagers. The cold temps make the yeast start to work a lot slower than an ale yeast at 60 or 70F. So a larger amount of yeast is needed to get it going as fast,or nearly so,as an ale.
Assuming a 5 gallon batch, ya, you are probably a little low on yeast. However, lagers can take a while to start showing "visible" signs of fermentation. You have pressure in the airlock, or check you gravity? You could use the tasty method and just slowly up the temperature every few days til its done.