Congratulations on being open to seeking help. This needs to be acknowledged, especially because you were previously reluctant to seek help. This change in your attitude is a very encouraging step and it shows positive emotional growth.
Your brother and father apparently did not treat you well. Your brother purposefully said things to hurt your feelings. Here is what you have to keep in mind. He most likely behaved in such a manner because he had his own problems and insecurities. His words damaged you and to some degree shaped your self-perception. The negative perception stuck with you and it affects your self-esteem and how you interact with others in relationships.
Your father did not show you the attention that you needed and deserved. The message that he may have inadvertently sent was “you don’t matter” or “you’re not important.” Children who have been emotionally neglected by their parents often report feeling that way. It is unfortunate and unfair but try to understand the whole context of the situation. Your father may not have been emotionally ready or able to give you the proper attention. Perhaps he did not know how. Without knowing more about your personal family history, I can only speculate but one thing is for certain: it is not your fault.
Everyone has difficulties in life to one degree or another. Your current challenges are self-esteem and relationship building. Both are very common problems. A good therapist could assist you. A therapist can examine your thinking to determine if your opinion about yourself matches reality and if not, teach you how to think logically and rationally. He or she can also advise you about how to develop healthy relationship skills. A little guidance can make a world of difference. The find help tab at the top of this page can help you locate a therapist in your community. I hope that you choose help over self-harm. Hurting yourself is not the answer to this problem. It is self-destructive and it will not help. I wish you well. Please take care.