Deodorant problems, really annoying?

ok so this is kind of stupid question i dont know why im asking this, but its actually annoying what im about to tell you, so i have been using this same deodorant for the past 6 years, im a guy by the way if that helps with the situation, and its called arrid xx, it smells good but the problem is this when i put to much under my arms, it turns into little small , and starts to fall from under my shirt, and its so annoying, but about 2 years ago it didnt do that, but then when i put to little of it on, it does the same thing, so it has to be just right, or if its not i have to wipe some of it with a piece of tissue, its really annoying, i dont know why this doest it, so can some one explain why this is happening, anyone?