Hi, I am a 19 year old male, just recently I had oral sex with my current girlfriend, I have been getting canker sore in my mouth. As well as swollen lymphnodes under my jaw. This happened just three days ago, my headache has gone down.. but I am worried this is some form of STD. My girlfriend said she was checked up just about a month ago, results came back negative, but they were only for two types of STDs.. She had Mono around last April, I was wondering I have possibly contracted it from her. Well I hope you respond quickly. I am extremely worried.