Admitting to my mom I'm having sex

Hi , I'm 17 years old and me and my boyfriend recently started having sex in January . He was my first and I wouldn't want to share that moment with anyone else but him . The scary part of the situation is deciding whether or not I should tell my mom . She's not really strict but she does not play when it comes to me having sex . I want to let her know but I'm terrified, what should I do?