I want to have sex with my bf but I'm afraid that I will get preg, is it safe to use condom in sex to prevent pregnancy?

Yes, Condom +. Safe means the condom somewhat protects him and you from an STD but has a 20% failure rate for contraception when used alone. Combine the condom with a vaginal contraceptive like VCF and your failure rate drops to 3%. Use the condom with a hormonal contraceptive and your failure rate is less than 1%. There is "safety" in those numbers.