advice please!!

you're a bit older than me. I'm 15. me and my boyfriend have been together for 9 months and he's always asking me to have sex. I want to so bad but I'm scared of getting pregnant. but i know it's a small chance. but I can't talk to my mom about BC. she would flip. & his penis is rather big for a 16 year old. & he's really immature. so I'm scared that if I have sex with him, it's all he'll want from me. he'll go CRAZY about it. more than he already is. he's never had sex and neither have I. I don't want him to break up with me because I won't have sex with him. but I love him and I want him to be my first. & I also don't want anyone to take his virginity. it would crush me. I just don't know what to do. please help me.