I've been where you are. I had gone so far that the Holy Spirit's voice was just a whisper. I didn't know how to return to Christ, or His calling. Until one day I prayed, I just told God that I wanted Him back. I didn't want to be in this depression anymore. You can never fix a relationship with someone you aren't talking to. Read through the Psalms. Don't just skim them, look for the deep meaning in them. Pray while you read them, stop and read a verse over if you need to.