What Causes Brownish Vaginal Spotting Other Than Periods?

iam 25 years old been ttc for 3 months now, this month i had loads and loads of symptoms and was almost certain that i had indeed fell pregnant, took hpt 's and are all negative, i would be either 13 days or 16 days past ovulation(today) depending on what my cycle would of been this month, well on saturday night i went too the loo and had loads of clear discharge with few brown dots in it, i checked for blood and nothing!! sunday morning (yesterday) i went to the loo in the morning did a test and again negative but when i wiped there was red blood. however since then it has come and gone come and gone, there is no flow what so ever, i do not need to wear a pad or tampon as its only when i use the loo that blood is on the tissue, looks like a period but no smell and i can usally smell mine (sorry) and like i said its only coming every few hours it not heavy but will cover the tissue paper. any ideas?