I'm by no means an expert but I can pass on advice given to me by my previous tutor. I'm sure someone will come along with a definitive answer soon.
I struggled with barre chords for a long long time, I used to try a few, give up, try again a month later. The advice I was given was firstly when positioning my finger across all the strings to make sure that the creases in my finger where it bends are positioned between strings if that makes sense, and practice. I practiced every day for 10-20 mins a time on barre chords and after a couple of months I'm now comfortable holding down all six strings. Just working on convincing the rest of my fingers to press where I want them now.
Hope that helps some way.
M.