Firstly relax, like you stated your periods are very irregular, this doesnt help the situation as working out when you ovulate is difficult.
is there any chance you could give us some dates? when you had unprotected sex? when you last started your period? how many days, roughly are there between periods?
I would say that brown blood is dry blood, i have the same situation my period are very irregular and i oftern get a brown discharge which i always worry about being implantion bleeding, but turns out to be just another period.
also looseing your viginity for the first time makes your body do many weird things and can upsett your period even more, also it could just be worry, cause your hormones are very sensative after sex, lossing v, etc..
my advice would be to take a test to takle the worries, and to be on the safe side! the go see your doctor about getting some BC, they will help prevent this situation, and regulate your periods for you, but please dont forget to always use a condom if you dont want to get pregnant!
Best of luck and keep us posted!
xXx
WELL THE BEST THING TO DO IS TAKE A HOME PREGNANCY TEST AND OR SCHEDULE A DOCTORS APPOINTMENT. BROWN DISCHARGE IS A SIGN OF PREGNANCY: IMPLANTATION BLEEDING. BUT IT COULD ALSO BE DRIED UP BLOOD JUST COMING OUT . BUT HEY IM NOT A DOCTOR AND THATS WHO YOU NEED TO SEE ITS POSSIBLE BECAUSE YOU DID HAVE UNPROTECTED SEX! AND GUYS DO PRE-*** GOOD LUCK