I have a boulevard wheat clone that's been in primary fermentation for nearly three weeks and am starting to be concerned as usually my batches are ready for bottling after 2 weeks. This batch still has a layer of foam on top and the airlock is still gradually bubbling. Normally I'd just let the thing sit and do it's thing until it's done and ready for bottling. However as I said it appears to still be going after 3 weeks. What's concerning me even more is the fact that there's more yeast at the bottom of the carboy than any batch I've every done. Long story short I'd like to get some input on what to do here. Should I just go ahead and bottle or should I let it keep sitting in primary fermentation until things have "settled"? I should mention that it's sitting in my basement during wintertime which means colder temperatures, though that has never seemed to effect any previous batches. Suggestions?