[Always *]

The hormone levels in your urimevtypically are not high enough to register a pregnancy until 2 weeks after conception. That's why you might have a negative test. If you take a second test, make sure it's 2 weeks after the 21st ok. I know this is scary. No matter what happens, everything will be ok. You mentioned a major stressor in your life; this is what could be causing the lateness, added stresses from stressing about being late could also delay it further. You may just miss a cycle, which isn't entirely uncommon. Whether you get a positive or negative test, if you miss your period you should the about seeing your doctor just in case.

Have you considered alternative methods of birth Comtrol like the Nuva Ring, IUD or pill? They're a little more reliable than condoms, less prone to human error and can eliminate future concerns like these. Many community health units sell birth control at a reduced rate (eg $5 for a Nuva ring instead of $20. $15 for 3 instead of $60, but that's the going rate in my country, I imagine it'll be more I'm the US bu not by much).