I need some advise

Jessicca
So I'm 15 and I'm talking to this boy but he's 19 we started talking back in August 2015 but I've known him for as long as I can remember because his dad is best friends with my step dad. Since we've been talking he's been out with 2 other girls, but he makes me really happy but he knows all the right this to say. He knows I'm still a virgin but we've been on about having sex and I want to I'm just nervous as. I feel like as soon as he has sex with me he's just gunna chuck me and I just don't know what to do. Plus I'm scared shitless of having sex for the first time. Any advise for having sex for the first time or if I should do it with him??