Re-stringing a guitar

Well this morning I broke my first string. I had tuned it to a drop-D to play something, and then tried to re-tune it back to the standard, the 1st string split at the tuning peg.
I'm not having problems with the actual re-string, I figured that out for myslef, did the lot of them since they needed doing
. Its what happened after the strings were put on. The guitar never wants to stay in tune for more than a pluck and the bridge has been raised considerably and looks on the verge of snapping off.
Did i get somthing wrong?
Thanks
I'm not having problems with the actual re-string, I figured that out for myslef, did the lot of them since they needed doing

Did i get somthing wrong?
Thanks