I’m struggling, PLEASE HELP!

I’m 17 years old, and in September of last year I became a Christian again after not being religious for 5-6 years. However, lately I’m finding myself doubting God and His existence. I read my Bible every night and do devotions every morning, but there’s this nagging thought in the back of my mind that tells me, “What if He’s not real? You have no physical proof He’s real, and if you do, so does every other religion. What makes you so sure He’s the one and only TRUE God?” Nothing is helping, and these thoughts are so strong that they make me feel so empty and sorrowful. If anyone has gone through the same thing I’m experiencing PLEAAASE LMK WHAT HELPED YOU AND GIVE ME ADVICE!!!!