16 day cycle! Help

I'm on day 16 of my cycle and having another period? Is this normal. I'm so worried. I used implannon for 6 years and had no period with it. I had it out on 28th July, my last period was my first which ended on 1st September and now I came on today 12th September! I am trying too Concieve which is proving difficult at the moment due too not knowing my cycle days now. Does anyone else have such short cycles?