Migraines and spotting on implant

Hi girls, I had the implant fitted last July after coming off depo injection after 5 years. I had no periods the whole time I was on it. As soon as I got the implant, my periods were back that month, and have been regular. I've had some spotting since, but not the past couple of months. I came off depo because I believed it was causing migraines, and I seemed to be right; I've had them much less often since coming off it. I'm suffering one today however, and I just went to the bathroom and discovered I'm spotting. My last period was last week. It might be relevant too that that period was a BAD one pms and mood wise. Could it be a spike or dip in hormones? Anyone else noticed this?