Is there any sex act in which I'm less likely to get an std?

Condoms Help. Condoms can reduce the risk of std transmission during sex, whether oral, anal or vaginal. However, they are not 100% effective as some stds such as warts can be transmitted outside the area covered by a condom. Mutual masturbation (not orally) reduces the risk as well, though not to zero. The safest way is to have both partners tested and maintain a monogamous relationship.
Sure, with self... Other than self masturbation, no. Thats pretty much it. If you have sexual contact with someone else, then you are at risk. Yes oral sex may be less risky for some things, like hiv, but for others like gonorrhea or hpv its still risky. Practice safe sex (condoms, etc..) always and keep safe and get tested frequently!