Quite simply, and unfortunately, if you've had unprotected sex, you may be at risk for an STD. The hard part is that most people with STDs have no symptoms so it's hard to know if you're infected.
There is a new online tool that sort of acts as a pre-screening tool before you head to the doc's office. Through a series of questions and answers, STD Wizard will tell you what you should get tested for when you do see the doc. I really like that you can print your results out and bring it with you so that you don't have to remember all the crazy names of things you may want to get tested for if need be. Also, if you're too embarrassed to tell your doc that you want to be tested for herpes, you can just hand over the sheet without H-E-R-P-E-S having to ever cross your lips.
Wondering what the heck all of this means? Then check out my posts that explain several STIs.