Having a sore throat after going down on my girlfriend?

Have yourself checkd: You can have a "regular" pharyngitis or you may have a more serious problem, like and std. Consult to your physician. He will recommend the apropriate test to find out what the problem is. Be honest and tell him what you did. Discussed this with your girlfriend and go together so she can check herself and both be treated in case of an std. Good luck.