If you are regularly menstruating previously, the first thing to be suspected now is pregnancy
. The spotting could possibly be post coital as it sometimes happens due to pressure effects in early pregnancy. HPTs do not always give positive result in early pregnancy owing to the low hCG
values in urine and these tests being less sensitive. Yet, avoid coitus and weight lifting and take bed rest
. I advice you to see a gynecologist for diagnosis and further treatment. Take care.