Plan b side effect

So I took a plan b about three weeks ago for the first time. I am aware of the side effects, I’m just a little concerned. I haven’t gotten my period in a week, (which I know may happened when taking plan b but I got freaked out and took a pregnancy test and it came out negative) but today I started bleeding thinking it was my period. Turn out the bleeding went away and I’m not on my period. I do realize that this may be a side effect of the plan b, however I figured that perhaps the bleeding would have happened more recently to when I actually took the plan b. It’s been three weeks since I took it and I just wanted to know if it was normal for me to just randomly bleed after a few weeks of taking it?