There are a few common early pregnancy symptoms, although not everyone sufferes from all of them. The most common ones are sore or tender breasts, sensitive nipples, frequent urination, nausea and like you mentioned before the obvious absent period. As for the brownish tinge of blood, it could be what you suspected, the start of your period. Or it could be implantation bleeding (start of a pregnancy). Unfortunately none of these things can confirm that you are pregnant, so you will need to see your doctor to get confirmation with a blood test.
Good luck