Ive Been Experiencing Period Cramps At Night Time For 5

Ive been experiencing period cramps at night time for 5 days now and my period is late by 4days. I have a slight increase in vaginal discharge, and nipples are a bit sensitive. I had 3 tiny drops of blood mid cycle almost 2 weeks ago. Tried home urine pregnancy tests all are negative. Can I still be pregnant? My period is usually always on time as I track it- usually 1 day early- 1 day late