Sounds like you could have several problems. First, you might hve a skin sensitivity to the minor amounts of fragrance that are in the disposable pads and that is one reason why the cloth works so much better. Second, you may be having a reaction to the plastic that covers the disposable pads. Third, if you are shaved and active you may just be getting rubbed/chaffed while wearing the disposables which are made to move and not cling. Asside from offereing reasons I'm not quite sure what to tell you, but figuring out which one would definately help to solve te problem. You can try and go with a fragrance free product, or go with one that is not covered in plastic (Stay-Free has both and I used it after both my pregnncies when I was not allowed to use tampons). You may also want to try getting a longer pad like the "ultra thin night time" pads, they ae longer so they grip better, move less and are nice and thin.
I hope this helps and if you would like some more detailed information about the alergies I have an expert in this field in my family that I can ask for you.