This is definitely not a silly question, and I’m glad you asked! If you and your partner have never had sex with anyone other than each other, it is very unlikely that you would have an STI. STIs are not created, only passed from one person to another. With that being said, if you have any doubts it can’t hurt to get tested! Getting tested for STIs is recommended at least once a year if you are sexually active.
When you and your boyfriend have sex, do you use a barrier method such as a condom? I ask because using condoms also helps protect against STIs. Hope this helps!
That all sounds great! If you want a helpful resource for information on safer sex practices and getting tested, this article has a great overview: Safe, Sound & Sexy: A Safer Sex How-To