Hello, I would be happy to help you with your question.
At about the time of ovulation, there is a brief, abrupt drop in estrogen
levels that is sometimes associated with bleeding. This might explain the midcycle brownish discharge. Also, it is not uncommon to have a little bleeding from the cervix
with intercourse. The combination of these two things could explain your problem. And yes, if you had conceived, the test would not be positive until at least 2 weeks after conception occurred - you might check again one week after the last test.
I hope that this helps and good luck!!