My bf is cheating on me with me

Tia • 16 year old volleyball player who's living life to the fullest😋
I need help! So I have had a feeling that my boyfriend has been cheating on me. He never lets me see his phone and won't give me his passwords to his social media. He cheated on me once and I caught him. So to see if he was, I made a fake profile and have been talking to him as her. He's called me beautiful and flirted with me a bunch. I asked if he was single and he said he was talking to someone. Then he asked to meet up and I said what about the girl your talking to? He said "I'm single aren't I?" And then blew it off. I'm hurt, I'm mad, I'm upset, and I could really use some advice. Please help.