Oral sex 6 days ago, could oral thrush show up as a result of oral sex?

It could. Oral thrush most often occurs when one is taking prolonged steroids, antibiotics or has problems with their immune system including diabetes. It is important to have your mouth and throat examined to rule out stds such as oral gonorrhea, herpes and human papilloma virus (hpv) best to use a dental dam with your partner if you don't know their infection status.