What is causing my sore throat???

Hi there! I’m a 22 year old virgin who is dating an older man for a little over half a year. We are monogamous and are not seeing other people. We don’t have intercourse but we do engage in oral sex. When we first started doing this, (two months into our relationship) I never felt sick ever. However, in the past 2 months, every time I give him a blow job I get a sore throat. Sometimes I get “Cold like” symptoms, (one time I got strep + oral thrush but I don’t know if that was related to giving him a blow job, I just know that the sore throat is definitely linked.)

I currently have a swollen lymph node under my chin, runny nose and a slightly sore throat that hurts a little when I sometimes swallow, also my tongue feels odd on the sides like I may be getting thrush again soon.

My boyfriend has told me that he has regularly been tested before me and definitely doesn’t have any std’s. So what could be causing my sore throat? Especially since it wasn’t an issue in the very beginning.