He broke up with his girlfriend a couple of days before we started dating, and he said he wanted to keep it a secret because of the fact that all of the rumors spreading around our school is what broke him and his ex up. I don't mind keeping it a secret, but when I'm hanging out with my friends it's hard not to act like he's my boyfriend. Especially since we're thinking about becoming sexually active soon. Do you think I should tell him to make it public? Is it normal to stay secret but be in a relationship serious enough for sex?

Answer: Too long!
Think you might find he's either still dating his ex or has another one he's told to keep his relationship secret with.
Grow up - he's using you!!
An old trick that one!