Im regular with my cycles and I always ovulate 14 days before my next period . I ovulated on September 14and that day I had unprotected sex on the next day after ovulation on September 15 I also had unprotected sex. Today is September 30 and I still haven't got my period so if I don't getot today Iim three days late and its 16dpo and I got a negative on a hpt (first response) on September 5 I had some cramping a bit of spotting but it went away after a few hours and ever since that day my lower back hasn't stop hurting. I've had also been very sleepy during the day when before I wouldn't take a nap during the day but now is like I need it . What's happening ? Can I be pregnant even of I got a negative ?

Three days late is too early to test.

Wait until your period is at least 2 weeks late, then test using first morning urine.

False negatives are very common, especially if you test to soon, which you did.

Good luck.