I'm awfully sorry for your loss, but I really doubt that death would be reuniting.
There is no certainty when it comes to death, no one can tell you for sure that death would allow you to see your boyfriend again. What if you went trough with it and death was the end of life? There was no afterlife and no chance of ever seeing him again? That's an awfully big risk that I don't think you'd be willing to take.

You have your whole life ahead of you, I'm sure if your boyfriend were able to see you now he would urge you not to commit suicide as he would probably regret it himself. I understand that it's hard and you miss him, but killing yourself would make things a lot worse.