I had unprotected anal sex with someone a few times who I know was a virgin, am I safe from any stds/stis?

If you dont have any and your partner has none then the risk is zero. STD just dont spawn out of nothing.

Virgins are not immune to getting stds. Any one that has unprotected sex can get an std.
If the person you had sex with doesn't have any stds then you're not going to get an std.
If you're going to have sex, ask your partner to use condoms, they can help reduce your chances of getting an std.

Dunno