Look at the screenshot that I have just made. So look at the average position and quite popular query! Why do I have such low number of impressions?
That average position shown by Google web master tools doesn't necessarily 100% accurate.check your actual position by conducting manual search in Google or using any serp checker.
Check SERP of your website manually for all those keywords on which you had good position. Google Webmaster Tools may show wrong data but not always.