The first thing I would say is don't feel bad about your feelings. They are what they are, and you and everyone else has to cope with them and be honest about them. There is nothing wrong with you or your feelings - this is part of how you are coping with what happened. It is entirely understandable that you would not want close contact even with a sister you love: contact and touching is a rough thing for lots of survivors (me included). It doesn't mean you are losing opportunities or ruining things - you are still finding your way.
Have you considered writing your sister a letter saying whatever it is you want to tell her? Another boy a bit older than you did that, as I recall, and his story about it is on the survivor forum somewhere.
Hang in there,
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)