I was considering getting felacio from a girl i know(don't know her sexual history) she said she's never had a cold sore, how common is sti transmission? when i was younger i never really thought about it, now i'm older and worried to get something?

Oral sex carries STI risk, but far lower risk than for vaginal or anal intercourse. The main risks are gonorrhea, herpes due to HSV type 1 (the main cause of oral herpes), and nongonococcal urethritis (NGU), probably often due to normal oral bacteria and thus not an STI in the usual sense. Slight risk of syphilis, near zero risk for HIV or chlamydia.