When I was 14, I had the same questions. That's completely healthy. So what happened was, the Holy Spirit challenged me back: Holy Spirit: How would you know if ANYTHING was real? Like how would you know if the screen in front of you is real? Me: Because I can see it, I can feel it. Holy Spirit: Your eyes are one of your five senses. Touch is one of the senses, too. That's the same with Me. You know I exist because you can sense me. You can feel my presence. Another time, I tried to see what happened if I stopped believing in God. But within a few seconds, I couldn't, because I could feel His presence so strongly with me, and I couldn't deny He existed.