Question about the TERMINATOR STORY?

Good question. What I always wanted to know was how was John Connor conceived in the first place....If Kyle Reese was his father. How was John conceived if he was the one who sent Kyle back? It's like saying the future happened first. How was he alive to send Kyle back? Did John have a different father the first go around? Great movie.(one of my all time favorites)....but a lot of holes in the story.