Long Lasting Cough After Giving Fellatio?????

Patient: I have been seeing a guy from May till early September. I had ggiven him fellatio In July and he claims to have never been sexually intimate with anyone before or during being with me so I shouldn’t have an STD. However, about a month later in August I began to get this deep-throat tickle that causes me to dry cough and I have ever since. So, I was wondering…..what can this possibly be???? Do you think this is a psychomatic problem for being anxious or is this something to look into…….thanks in advance. It’d be nice to know if this was serious or not.