High E string suddenly breaking more often. Am I doing something wrong? Been playing guitar for years now and having no problems and suddenly the high e string on my guitar (Epiphone SG) is breaking more often. Most recently I was restringing my electric guitar (Elixir strings medium)  perfectly fine and all the strings are on apart from this last. I tune up slightly and stretch the string a little to release tension and then I tune up to high d and it's fine but as soon as I hit eb it snaps at the tuning peg. Third time this has happened, once whilst playing and other two whilst restringing. Am I doing something wrong?

I am tuning to E Standard A440