I need help with my boyfriends death?

Okay, I'm 16 years old and I was dating this guy. When I first met him he told me he had melanoma (skin cancer), he got really sick and they found that the cancer spread to his brain. He died two weeks ago, and I don't know what to do. He meant so much to me, and him dying has killed me. I cry myself to sleep every night because I feel so alone. I never sleep at night because I have nightmares about him dying, and then I wake up even more scared because he's actually dead. I dont know what to do. I can't get over him, I think about him all the time. I always hear him saying that he doesn't have much longer to live, and it's as if hes still alive. I miss him so much. I feel like everyone around me is dying. I've lost a lot of people very close to me due to cancer. I miss him so much. It was such a hard relationship, because I always knew he was going to die. I don't know what to do. I hate waking up and being happy for that one second then everything hits me because he's gone. He was my best friend, and I feel lost without him. What do I do?