I'm going to finally tell my friends (on messenger) they don't value me as a friend but during exam season
Did this make your friends think of your relationship with them any different?
Yes, he saw me differently when my exam scores are good.
You should be honest how you feel when talking with your friends. Nobody is expected to be used and thrown away just for their exam scores or helping the other person.
I just never got the chance to tell him how I feel.
Well it is never to late to let them know your feelings. Whether they listen or not, it may make you feel better to simply be able to get your emotions out and know you tried.