"For the last two months, I've had suspicions about my boyfriend cheating. Recently, I found proof of him cheating. What's the best way to confront him with this evidence?"
If you found evidence of your boyfriend (or girlfriend) cheating and now want to confront him, frankly I say don’t waste your time and energy. Really, what do you think you’re going to get when you confront him with that evidence? He's either going to deny it, downplay it, or admit it.
If your boyfriend denies it, then of course he is lying, and you will likely spend crap loads of time and energy trying to get him to admit it. And what’s going to happen then? You’re going to be even more upset and likely just leave him.
If he just makes excuses for the cheating, you’re not going to believe him. Again, you are likely going to spend crap loads of time and energy trying to get him to admit it was all for a selfish reason. And in the end, you’re just going to leave.
If him admits it, then what? Say his reason was because you weren’t giving him enough attention or sex. Are you still going to stay and now give him the exact amount of attention and sex he wants, forever and ever, or at least until one of you is dead? You really think you’re going to even be wanting to have sex with him again right away? Of course not. You’re going to be miserable.
And here’s a sad fact: Once a person cheats on you, a seed of doubt is planted that will eventually resurface whenever that person exhibits even a bit of shady behavior, no matter how much you really want to trust them again. It's like dating someone who is cheating with you.
Even if that person leaves their partner for you, as soon as they do something shady (such as start coming home later than usual with no good reason or not wanting you to see who calls and texts them), you're going to jump to the conclusion that they must be cheating because they did it once when they cheated with you.
In the end, the result is either you’re going to leave or stay but be miserable. There’s nothing that’s going to make you feel better by confronting him. It’s better to leave. You can even just leave the evidence with a note: “I hope you and (whatever that person’s name is) will be very happy together. After everything I did, it still wasn’t enough. You obviously weren’t happy with me. Take care.” Then if possible, delete him out of your life and move on.