Why Do I Have Bleeding After Having Completed Menstruating?

Hi I have already had my period two weeks ago but it's weird today I have been feeling weird when i go to the loo and wipe myself i see a little bit of blood? i have take a pregnancy test yesterday and came negative i feel like going to the toilet every 20 min. i have never been pregnant and i have been with my partner for 8 years now and were each others first what could this mean?