It's not you who isn't sharing anything. It's the others. While some ultrapeers are obviously sharing a couple of thousand files with their leafs (60%+ of all searches are forwarded) others don't seem to share anything at all (only 5% or even less of all searches are forwarded). The number of ultrapeers with leafs that don't share much at all is rather high (>50% - just a guess). While saving you lots of bandwidth it also indicates that there are still far too many freeloaders in the network.