Imaginary Friend?

I feel invisible, non-important, useless to my friend. They make me feel that way, but I know they don't do it on purpose. They are going through tough times, and it seems nothing I say or do is right. I feel like nothing I can do/say will be good enough..and it scares me. They scare me. I've told them that they can trust me and talk to me about anything, but instead they never reply to my texts or anything..and now that they feel completely lost, I've let them down..not purposely..but its the simple fact that I did..and now I don't know what to say or do to make them feel any better..All I want is for them to be happy.