Welcome to the forum.
Although I have no direct knowledge of HIV epidemiology in Colombia, I'll bet the chance your partner has HIV is quite low; and when a woman has HIV, the average risk of transmission by vaginal sex has been estimated at 1 in 2,000. That's equivalent to having sex with infected women once daily for 5 years before transmission might be expected -- which is why many spouses of HIV infected persons never catch the virus. Second, your symptoms do not suggest HIV, which does not cause runny nose and brief sore throat.
Third and most important, a negative antibody test at 6 weeks is virtually 100% reliable (and 1 day short of 6 weeks makes no difference). How many cases I have observed is irrelevant; my and Dr. Hook's advice has never been based only on our personal experience, but on published data and other solid science. In case you are interested, here is a thread that explains the discrepancy between test reliability at 6-8 weeks compared with frequent official advice to wait 3 months: http://www.medhelp.org/posts/show/1347755
As for other STDs, testing for gonorrhea and chlamydia is reliable any time more than a few days after exposure. However, 3-4 weeks is too soon for all STD blood tests. Six weeks is about right for syphilis, and 3-4 months for herpes. However, in the absence of symptoms, your exposure does not warrant testing for any STDs other than gonorrhea, chlamydia, syphilis, and HIV.
Bottom line: Almost certainly you caught no STD. If you want a bit more certainty about syphilis, you should have another blood test.
Regards-- HHH, MD