Welcome to the forum.
No worries; you don't have HIV. Your risk really was too low to even have a single HIV test. Here is why:
The odds a woman like your partner has HIV is zero or close to it. Being in New York could elevate the chance she is infected, since heterosexually transmitted HIV is more common than in most other cities -- especially if she is African American. But even then, it is unlikely she has it. And if she were infected, the odds of catching HIV from only a single episode of vaginal sex are very low, probably on the order of 1 chance in 2,000; and oral sex is virtually zero risk. Finally, your symptoms do not suggest a new HIV infection, which does not cause gastroenteritis as the only problem; as you seem to know, you didn't have any of the usual symptoms of ARS.
But most important, your negative test results, especially the one at 7 weeks, prove you didn't catch HIV. A negative rapid test, either fignerstick or oral fluids, is just as reliable as a lab-based test. Something other than HIV is the cause of your gastroenteritis.
In case you are wondering why a 7 week test is sufficient, and you don't need another test, despite common advice about testing at 3 months, take a look at this thread:
http://www.medhelp.org/posts/HIV-Prevention/-A-Question-on-Testing/show/1347755
So you definitely can move on with no worries and no need for further testing.
I hope this helps. Best wishes-- HHH, MD