It does sound like your boyfriend's behavior is cause for concern. While it is possible that there may be a reasonable explanation for his late nights and second phone, his unwillingness to be forthcoming with you is troubling. As the old saying goes, where there is smoke, there is often fire.
I cannot stress enough the importance of trust in any relationship, particularly a romantic one. If your boyfriend has betrayed your trust, whether through infidelity or deception, it may be time to reevaluate the future of your relationship. It may be painful, but it is better to confront the truth than to live in denial.
However, I must also caution against jumping to conclusions or making accusations without evidence. It may be worth having an open and honest conversation with your boyfriend about your concerns, and giving him the opportunity to explain his behaviour.
Ultimately, only you can decide what is best for you and your well-being. Pray for guidance, seek counsel from trusted friends and family, and trust in God's plan for your life.