When I started playing I remember having a big problem with the F major chord. I think its a very common problem for beginners. Try using your index finger in different ways, i.e I tend to play F major almost with the side of my index finger if that makes sense. Another solution is to play a partial F major chord until you build up strength in your index finger. Instead of your index finger barring across all six strings, just barre the high E and B strings. You will eventually want to learn the full barre because you will need this skill in future for full barre chords, but this may get you started until you build up strength.

Hope this helps.