Implantation Bleeding??

So my boyfriend and I use the pullout method (have been for a year now) and this is the first time I've been truly worried about being pregnant. I should have started my period by now and I swore I was going to last week because my moods were all over the place, I was crazy. About 4 to 5 days ago I noticed that a brown discharge like old blood had started so I assumed it was the beginning of my period, but this spotting was so light I got by with a panty liner a day. The spotting has stopped now and I haven't had anymore signs or symptoms of either my period or early pregnancy. I'm worried that this might be implantation bleeding bc of all the articles I've read. Has anyone experienced this and happened to be pregnant? I need some advice!