Wait until two weeks after your missed period for the most definite results.
It can take a while for it to regulate. I got mine at 8 months also and between that and when I got pregnant at 13 months pp I had 3 periods and one of them was only spotting.
I got my period when my daughter was around eight months as well she is now 13 months and my period is still all over the place. They say it can take awhile for it to get back into a schedule.
It could be to.early for the test to tell waot a few days and take another.. Same thing happened to me i was pregnant.