It could be that your splint needs to be adjusted - your jaw may have shifted a bit due to it being worn - as it should. Weather changes such as is temperature, dryness or humidity could affect it but that would also imply that you have some arthritis or degenerative changes affecting the joints - similar to that of knees, fingers, wrists, etc that hurt. I'm not sure about sugar - it kind of sounds like the old saying that chocolate and pizza cause acne - but I guess if you did have some problems in metablolizing or processing sugar it could produce other reactions. For the most part though I think tmj is a structural issue - in other word its influenced mainly by the functioning of the teeth, jaw, discs, joints and mucles.