Pipe cleaners are the least expensive part of this hobby--be generous with their use. Periodically push a pipe cleaner through, then tamp. Relight if necessary. It's also possible that you may be getting some saliva down there. Sip your pipe slowly--don't puff. And, let your tobacco dry for a bit before you pack it. And I do mean dry. Very dry. If it crumbles into dust when you push down on it, you've dried it a bit too much, but anything short of that is okay. Even if it makes a slight twinkly sound. Tobacco that is too moist is a particular issue with many aromatics, since they often contain humectants, substances that are intended to attract moisture.