opinions and help please!

[tbl90.livejournal.com]

Hi I'm 18 yrs old, Ive been dating my boyfriend for about a year now, I decided to have sex and lose my virginity to him last week and we used a condom and im on birth control. I did not bleed at all but felt some pain. We had intercourse three more times over the next 2 days(always with a condom) but it still felt a little unpleseant. Today (about 5 days AFTER the FIRST time we had sex) I noticed a really dark brownish, almost black discharge releasing from my vagina and it wont stop, my period isnt due till 12 more days or so. I am very afraid to ask anyone and tried looking online but i would really appreciate if i can get some help form this forum. I am starting to worry that this discharge could be due to implantation and that i could actually be pregnant (from all i read online), and i was told its too early to take a pregnancy test right now. I really don't know what to think, please help me.