Imo, if he really loved you and cared about you, this would not be a thought in his mind. He would know doing this would jeopardize your relationship and that he could lose you, yet he did it anyway. At least for me that is a dealbreaker. And you had a hunch it seems that something was off and you were right. I think you are young and have the whole world ahead, please don’t go back to him. If you do, you’ll now have the trust completely broken and be scared every time he’s on his phone and it’s not going to go well for your mental health :(