Bad news: everything is temporary
Good news: everything is temporary.
Sometimes God does questionable things but its for the best. Right now, you are in a tough spot and I feel your pain. Same thing happened to me 3 years ago as well. I felt like shit but later I realized my worth and thanked God because he got rid of 2 fake people in my life. Your gf cheated on you meaning she was pretending and your best friend is dating your ex even after knowing what happened. If he was your best friend, he would have never do this.
TRUST ME! Just prepare for your exam and forget about them, I know its hard but hit the gym and keep your mind busy. Sucide will just make things harder to your parents and you don't gotta punish your parents like that. Take care of yourself and family while focusing on the grind.
Cut ties with them(with your bf as well if he is dating her) and work on self improvement. There was no love in between both of you anyways.