when i bend upwards on one of the high three strings, the string above it occasionally slips underneath my fingers doing the bend, causing me to be bending two strings at once. what can i do to avoid this?
Make sure that the string hits your nail, and thus doesn't touch the other string. You will always bend 2 or even 3 strings at the same time, you just have to make sure that the string you want to ring out rings out and the other strings don't.
try not to let the strings above the string you are bending go under your finger nail. First reply was right, you are going to bend more than one string majority of the time, you just gotta try not to let it make any sound you don't want.