Im sorry but I really dont think sperm can swim through your tampon, and usually implantation bleeding doesnt happen til a couple weeks after conception (i believe, but I could be wrong)... But brown blood means old blood, which was probably left over from your period (which happens from using tampons, blood gets stuck up on something or something like that)... But yea about the whitish discharge, maybe you have a yeast infection? But I really dont think you are pregnant, since you had your period and was wearing a tampon, and the fact that you said you didnt have sex and that you are a virgin....