TeenHealthFX knows that this must be a very confusing and painful situation. What this family member did to you is wrong. You do not specify what kind of abuse but from your question about it feeling good, TeenHealthFX suspects it was sexual abuse. Often adults with misplaced sexual thoughts and violent tendencies target young children because they are trusting and do not know what is right or wrong. They often create a trusting relationship with the child and then use it to their advantage along with their size and strength to hurt. Understand that it is not your fault and that your body and your trust were violated.
You ask if it is supposed to feel good. If you were stimulated sexually, then it probably did feel good physically - your body responded to the physical touch, but emotionally it probably left you feeling used, violated, guilty and angry. It is not true that if your body responded to the physical trust that it means that you asked for it or in any way wanted it to happen.
TeenHealthFX believes that you need to speak to your parents. They may get angry with the family member for hurting you. If you do not think you can tell your parents, talk to a trusted adult or counselor. Once you verbalize your experience you will be able to start sorting through your feelings and begin healing. It is very important to tell someone. You may feel intimidated into silence but you must speak out. What happened is not right and will not go away with time. Bottling up your feelings may prevent you from creating new relationships and becoming close personally and intimately with others. It will be beneficial for you to seek counseling to help sort through your feelings.
If you would like more information or help you can call Rape, Abuse and Incest National Network (RAINN) 1-800-656-HOPE (4673) 24 hours, 7days a week. If you live in northern New Jersey and would like help finding a therapist you can call the Access Center from Atlantic Behavioral Health at 888.247.1400.