guys, I don't know anything about the cousin issue, but if she says it was a long time ago, then leave it. She came on here looking for advice, not to be insulted. She gets enough of that by her boyfriend. If you can't help her, don't post.
Now, confused, I know exactly how you are feeling. In 2001, I was with this guy, temporarily, who I thought I absolutely couldn't live without. He treated me like dirt around his friends but was all nice and sweet when we were alone. It was those times that made me want to stay with him. I thought maybe he'd change. Whenever I did try to break up, he'd cry. Like a fool, I believed he would change each time that happened. He never did.
Finally, he broke up with me and I was devastated. I tried committing suicide by taking a bottle of medicine and wound up in the hospital, all because I thought I loved him and couldn't live without him.
Afterwards, I missed him like crazy and cried constantly, but I kept going because I knew that it was just temporary. I got involved in activities to take my mind off of him. I read a lot and learned hobbies. Eventually, I came out of it. Now I am married and truly love my husband.
You aren't the only girl going through this. I know you are reading this and probably saying "This is different" or "They don't understand what I'm going through" or even "I can't live without him. You could, but I can't". Well, stop it. You CAN live without him. Yes, you will cry. Yes, you will miss him. Yes, your heart will feel like it is breaking everytime you think about him or even see him. But let me tell you, you WILL go on. You WILL get over him. Believe in yourself.