What kind of whetstone is it - natural, silicon carbide, other?
Clean it up real good and if that doesn't help it may be too fine a grit or it may be glazed and need to be lapped with wet/dry sandpaper. Another option if possible would be to buy a Norton silicon carbide stone from Home Depot and see what that does - they're about 6-7 bucks I think. Well worth it. If that does a better job, maybe you can use your old whetstone to do a final honing if its a finer grit.