Is this implantation bleeding? ?

Thursday night i had with my partner and we used a condom. (wast a virgin) on sunday night i noticed dark brown blood in my underwear! i have never spotted before and started my period about 10 years ago. I am around the time of ovulating. I havent felt pain, i was actuallly shocked. I doubt it has anything to do with my period as they are ALWAYS heavy and painful and i always cramp before my period comes. Not to mention i had my period about 2 n a half weeks ago. Do you think it is implantation bleeding? I have never spotted before so i dont know what spotting looks like.