I saw this before responding above. It does not change my opinion or advice.
Welcome to the HIV forum.
Responding first to the opening question, before I read beyond it: The "defintive" answer is that symptoms of acute HIV infection (acute retroviral syndrome, ARS) typically start at 10-20 days and generally last 2-4 weeks, i.e. until 6-8 weeks after exposure. Exceptions on either side of these times are rare.
Now I have read the rest. First, you describe a low risk exposure. The chance a partner like yours has HIV is nearly zero, assuming you are in the US or other industrialized country. Second, not only are your symptoms too late, but they don't really suggest HIV, which doesn't cause headache as the main symptom, and it just about always causes substantial fever, which you don't mention. HIV also doesn't cause nasal congestion, sinus drainage, nausea, or intestinal symptoms of the sort you mention. In short, there is nothing in your story that makes me think HIV is a remote possibility. Third and finally, back to the timing: yes, 10-12 weeks is definitely too late for HIV symptoms. Whatever you have, almost certainly it is entirely unrelated to your sexual exposure 3 months ago.
Since you're nervous about HIV, probably you should be tested for reassurance. This is not "code" meaning I really believe there is some risk you have it. I do not. You can expect a negative test result.
Regards-- HHH, MD
No need to reply to me again.
Just wanted to say thanks for helping put my mind at ease and that you are doing an invaluable service here. It must take a lot of patience as there are a lot of people who are stressed and worried asking for answers.
My only apprehension about being tested is because i hate needles or drawing blood and i'm not really comfortable in hospitals or medical facilities. But i suppose if i want total peace of mind i will have to get up the nerve for that.
But i'm feeling much better with your assurances and description.
I forgot to mention she had a clit piercing about a week or so before the sex.