“Why would my throat be itchy if I performed oral sex on my girlfriend and she’s a virgin?”
There is not a lot of information in your question so here are a few thoughts. Usually, if the itchiness and slight soreness goes away after a few minutes then it is not worrisome. However, if the itchiness and soreness is there a lot and gets worse with oral sex or just will not go away, then you would need to make an appointment with your care provider to evaluate the symptoms further.