corn snake digestion issue

Question
36" corn:  I bought a bag of small adult mice (frozen) in early December and they had quite a size range.  I sorted them and have been feeding him the smallest ones two at a time.  All going well.  This morning (5 days after feeding) he pooped.  The first mouse was partially digested, the second mouse not at all.  He has been very active and healthy until this.  The only other thing is that he has not shed in 4 months.  Suggestions?

Answer
I've never heard of a mouse being pooped out looking undigested. My guess is that he regurgitated the mouse (ie. threw up), but usually this happens within a couple of days after feeding. Was the mouse very slimy and extremely smelly? If so then it was most likely regurgitated. In any event, I would wait 10 days before feeding again, and then feed only 1 mouse and wait for it to be pooped out. The reason for the 10 days is that if it was regurgitated, you need to give the snake to build up the digestive juices in it's stomach.
I've also never heard of it taking 4 months for a she, especially since you seem to be feeding him well. Snakes shed their skin as they outgrow it, so a 3' long snake that is well fed should be shedding about every 45-60 days or so. In any event, there's not much that you can do to control that in any way.