What Causes Brownish Vaginal Discharge After Having Sex?

my name is kayla and i have the ovulation calender janurary 22-27th shows that ill be fertile. 2days before my ovulation started i had sex and my bf ejaculated in me. and on the 23rd he ejaculated in me and my most fertile day ont he 25th he ejaculated in me . and today on the 26th i went to the bathroom and a seen a lil bit of blood that was light pinkish/brownish and when i whipped samething but i know its not my period my period comes on feb 9