This is a complex situation. Your boyfriend seems to have an affinity for your friend and you can’t let go of their betrayal of you. You said in your letter that “the damage is done and it can’t be repaired.” This problem may be repairable but it will require a serious commitment to healing the relationship on the part of both you and your boyfriend. It may also necessitate couples counseling.
You are having thoughts of suicide but seemingly not because you want to end your life. Rather, the purpose would be to punish those who hurt you. Thus the motivation is punishment of the other, not to harm yourself. In essence, you want others to experience the pain and suffering you have endured. Your hurt feelings are understandable but your approach to dealing with them is not healthy. There are other ways to communicate your hurt feelings that do not involve harming yourself.
You say that your boyfriend makes you feel a particular way. Please keep in mind that no one can make you feel anything. Feelings emanate from within you. Your boyfriend may say hurtful and inappropriate things but the feelings generated as a result are yours. The fact that you feel inadequate because of his comments may indicate low self-esteem. Individual counseling could help develop healthy self-esteem.
Your boyfriend betrayed you. Now he cannot understand why you’re having difficulty coming to terms with what he has done. You essentially caught him cheating and he wants to remain in contact with the friend he cheated with. He cannot expect you to simply “get over it.” He has hurt you and if he wants the relationship to continue, then he needs to demonstrate, with actions, not words, that he is worthy of your forgiveness. Thus far there’s little to no evidence of him fully appreciating the pain that he has caused you. If this does not change, the relationship may not be salvageable.
As I mentioned above, you may want to consult a couples therapist. It would be the most efficient way to handle this problem. If your boyfriend is unwilling to attend couples counseling, then you should consider going alone, to an individual therapist. The individual therapist could provide you with the advice and guidance necessary to navigate this complex relationship.
If you feel suicidal, then go to an emergency room or call 911 immediately. The find help tab at the top of this page can help you locate a therapist in your community. I wish you the best of luck. Please take care.