Can you give an sti to someone then test negative

[aero2011]

Dear Doctor,

I know that this question may appear odd but they've been at the back of my head since I had my risk event.  If you could please help me by giving me answers and any specific facts in relation to STI'S to prove my theories wrong so that I can finally put this behind me and get on with my life I would be greatly apprecitive.

Last June I was working in America, on the last night I went out with guys from the office and I got quite drunk, which resulted in me receiving unprotected oral sex from a girl I met in the bar that night (she was not a SW).  I did not give her oral but did give here clitoral/vaginal stimulation using my fingers.  I showered after receiving the oral, not straight away but about an hour or so after.  I have a regular girlfriend of several years at home and have never done anything like this in my life at all.  
When I got home about 36 hours after receiving the oral I had some unprotected vaginal sex with my girlfriend.  I did not ejaculate and was not inside her for more than a minute or 2.  
5 days after the risk I went and had a full STI screen at my local GUM clinic.  The results came back all clear.  
I then went back about 15weeks after the risk and was re-tested, the results of which all came back negative.
I had started to put this shameful event at the back of my head and get on with my life but my anxiety started to get the better of me and I started to think about the event again and i then started to generate questions in my head to torture and punish myself such as:
1: could I have transfered an STI (in particular HIV) to my girlfriend because i had unprotected sex with her so quickly after the oral risk (36 hours), even though I went on to test negative in 2 tests, because sti's could have still been present/reproducing on my penis or in my urethra after that length of time, but i never tested positive

2: can you be a carrier for an sti and not get it yourself

PLEASE HELP

[aero2011]

Doctor,

Thank you so much for reading my last reply and actually commenting back to me about it, it really was kind of you to do that.  

After the emotional stress and pain that my Drunk Risk has caused me, not to mention the fact that its given my anxiety an opportunity to start creating "what if" theories such as a virus living on my penis for over 30hours and then infecting my girlfriend but not infecting me, I will never do anything like it again.  

I am still battling with the what if theories but i am working on accepting that it is the anxiety getting the better of me and that the theories are not true, there is no proof that it is possible and that its my anxiety which needs dealt with and nothing else.

Once again thank you for helping to disprove my theories and helping me to try and move on.
  

[Dr Sean Cummings]

Morning

I wouldn't be too guilty for too long - there are other things to worry about. My point mainly is that when people stray they do need to take that seriously and responsibly and test before they resume their usual relationships.

I would absolve you of "guilt and shame" now.

Best wishes, Sean

[aero2011]

Dear Doctor

Thank you for answering my question and re-emphasing that I do not have an STD nor could I have given one.  I have no excuse for what i did at all and i have punished myself daily for my actions...its my guilt and shame i have to live with for the rest of my life and thats not a pleasant punishment but its one i desserve i know...

[Dr Sean Cummings]

Good morning

1: could I have transfered an STI (in particular HIV) to my girlfriend because i had unprotected sex with her so quickly after the oral risk (36 hours), even though I went on to test negative in 2 tests, because sti's could have still been present/reproducing on my penis or in my urethra after that length of time, but i never tested positive

If you tested negative then you were not infected and did not have an STD (for which you were tested) and therefore cannot have passed it to your regular partner. I think it bad manners to cheat, then have unprotected sex with your regular partner, but obviously thats a matter for your individual sense of personal ethics.

2: can you be a carrier for an sti and not get it yourself

You can certainly have an STD and be a carrier without having symptoms - BUT - importantly for you, you tested negative and so we KNOW you do not have an STD

So on this occasion you seem to have got away with it, Be careful. It's not fair to put others at risk.

best wishes, Sean