Slight pain in opening of penis, is it an STD

[plbAuburn]

The other night I awoke sleeping in an awkward position, on my stomach, with a lot of weight on my penis.  It was painful, but the pain didn't subside for a while as I laid awake in bed.  The tip of my penis was very irritated.  I finally fell asleep, only to wake up in the morning with slight pain in my penis at the opening.  It lasted, on and off, throughout the day.  I also had slight pain when urinating at the tip of my penis, but no burning sensation.  There is also no redness.  This pain is still on and off.

I've read about chlamydia, and I know this type of pain is a symptom.  My concern arose because my girlfriend, who I have been in a monogamous relationship with for about a year and half (and 100% faithful, I can assure you), currently has some possible STD symptoms (slight burning when urinating, irritation), but it could also be just a yeast infection.

I'm not ruling it out an STD as a possibility, but I've only had unprotected sex a three times, once before I started dating my girlfriend, and twice with her when we first started dating.  Since then, my girlfriend and I use condoms every time, and she tested negative for all STDs months after the last time we had unprotected sex.  If one of us was infected when we started dating, she would have tested positive then.

I'm confused because if our mutual symptoms are STD related, why are the symptoms showing up so much later, how could we possibly be infected now if we weren't after the unprotected sex, and why did our symptoms appear at the same time after months and months of protected sex?

I admit, I am paranoid, but there is still doubt in my mind that we coincidentally both have a yeast infection and penis injury, respectably.  

I guess I need to know if there is any possible explanation for the pain besides an STD.  

[gracefromHHP]

If you both tested negative for std's and haven't been with anyone else then it's not likely to be a std.

If you have pain, go and be seen. Same with your gf. she shouldn't attempt to self treat at home - she needs a proper exam and testing done.

grace