What Causes Swollen Superficial Cervical Lymph Nodes?

I have a slighty swollen superficial cervical lymph node. It is about .5cm...its not painful at all. It is on my left side. I can feel it everytime i turn my head right...buf i cant see it.I read that its called a shotty node. I have no symptoms at all. No weight loss,nigt sweats,fever etc. i had unprotected oral sex last june. I am wondering is it hiv? Also my girlfriend had chlamidiya and we were having unprotected sex so when she found out i took the meducine with her just to be safe. The doctor said wait a week before we had sex again so the medicine could work but we didnt.. Could it be chlamidiya as well?