Could The Brown Discharge I Noticed After Taking Primolut-N Be Implantation Bleeding?

Please, I started my period on 10th of December, having 23 days cycle, I ovulated on 17th and I met with my husband, I was trying to have a baby, then I met a nurse ,she said that my periods are not regular that she will give me primolut n that I will take it for ten days and stop,then I will see my period, if I didn t see my period that I will come back on 8 days to do pregnancy tests. So I started taking the drugs on 25th which I will stop on 3rd january.so on 29th December being five days of taking the drugs, I saw drop of blood, I thought it is my period coming ,I wear pad, but in the morning, nothing stained on the pad, I checked my self, it has turned to brown discharge, am confused, is this implantation bleeding or what, should I test for pregnancy..am confused here.