Ok, there are two things I think are possibly happening.

1) Your snake is shedding once again
OR
2) Your snake did not shed off the skin on the underside

Check to see if the snake is dull in color, and if the eyes seem to be slightly turning a cloudy or milky blue color. This tells you that your snake is shedding once again. This can happen, even after your snake JUST shedded it's skin. This has happened to me before: My King snake shedded and was fed the normal 1 large f/t mouse, then the next week I fed him the same thing and the very next day his eyes were becoming a cloudy/milky blue color, and there he goes into shed again. My BP recently shedded about 3 or 4 weeks ago because I fed her 2 large f/t mice, which she normally eats just one. I think feeding her two caused her to go in shed, but still don't really know how.

If your snake does seem to have not shedded the underside, soak the snake in warm water for 15-20 minutes and put the snake back inside the enclosure (raise humidity, 60%-70% so the snake can shed it off better) and see if the snake sheds the skin.