Implantation Bleeding ?

Ju

My last period was 1/2/18 - 1/6/18. On 1/8 and 1/9, I had medium to light spotting (brownish color, and that has never happened to me after a period). Today, 1/13, I noticed light-pink spotting (I even used a q-tip to make sure I wasn’t seeing things). I have never been pregnant OR on birth control. Implantation bleeding? When should I test?