I Need Help!

Patient: I am 16 years old. My last period was on Dec 13. Me and my boyfriend (Ex now) had sex on the 22 23 24 and the 27th. i am 16 days late for my period. i had spotted only one time about 2 weeks after the last time we had sex. it was only one trip to the bathroom.. what are the chances of me being pregnant? I have taken 2 pregnancy tests earlier but they were both negative.