How do i deal with my extremely creepy grandfather?

My grandfather creeps me out. I just lost about seventy pounds and everyone tells me how attractive i am-especially my grandfather. He likes to buy me things, like underwear and lacy bras. I just learn that he did the same thing with my mother when she was my age. A couple weeks ago, i gave him a hug goodbye and he started to kiss my neck. He said that he was just giving me a taste of what guys are going to be doing. He is my mother's and my golden goose and if i hint he creeps me out, my mom brushes it off. My sister and i both think he is creepy. How do i deal with this. He favors me quite noticeably and i'm kinda of scared because i don't know what my mom would do i told her. Please help me someone. I don't know what to do.