Let me start with two comments- first, congratulations on your commitment to safe, condom protected sex.  That will do much to reduce your STI risk which tends to be far higher with genital-genital contact than with receipt of cunnilingus.  Second, your assessment of the internet is right on target- so much of what is there is wrong, making rare events sound common and suggesting that the risk for HIV and STIs is far higher than in the case.  The fact is that most people do not have STIs and that even when a partner is infected, most exposures do not lead to infection strongly makes it unlikely that you were infected.  With regard to your HIV risk, this is a very, very uncommon event.  The CDC, whose estimates tend to be conservative, estimates that, if your partner had untreated HIV infection, your risk for infection would be 1 in 10,000.  In other words, IF your partner had untreated HIV, which is unlikely, the odd are 99.99% that you would not get infected.  

Regarding your symptoms, abdominal cramping, vaginal burning and discomfort is not normal and if this persists, I suggest you see your Gyn for evaluation, not because I think you have an STI or HIV but because it is important to evaluate these symptoms, particularly if they are getting worse or not improving.  I would repeat your test for a UTI, suggest STI testing for your peace of mind (FYI, if these symptoms were due to HIV, your test would be positive- when symptoms are due to HIV, tests are always positive)

I hope this information is helpful.  If any part of this response is unclear, please use your up to to follow-ups for clarification.  Once you see your GYN, if you choose to do so, please let us know what she/he says.  EWH