Explaining STDs while sexually active

I have general warts. I don't know how to bring this up in a conversation so I usually say I don't want to have sex or that I'm on my period but it's not something I could hide forever. I'm afraid of how I'll be seen or if I say it, it will spread out to others. I'm mostly afraid of giving it to the other person. Any advice on how to communicate this or tips on having safe sex with genital warts?