Just a thought, but you might want to gradually work into a steeper decline. Start with a 1-riser decline (I'm assuming you're using a step as a bench, if not, this may not apply) and move on to two risers once you feel more stable. You also might try lowering your weight for a while. I know, I know, going down in weight sometimes feels like backtracking, but I think it can help you work on form and work back up again to a higher weight.