Am I Safe From Pregnancy After A Negative Pregnancy Test, Taking Primolut N, And Having Light Bleeding Afterward??

Hi, I have missed periods on 12 Feb , I did unprotected sex on 14 again , and on 18th Feb I did urine for pragnancy, which is negative on 19 I did beta HCG which is also negative, then I was prescribed primolut n for 5 days 2 tablets a day, during primolut on 24 Feb I did test for urine strip which is also negative, and on stopping of primolut n on third day I started bleeding which has last for 3 days and now stoped, although it was a little bit lighter bleeding. Do I have to worry about pregnancy or I am safe. Please respond.