I had one as well it lasted a little over a week and haven't had one since I also didn't get periods before pregnancy due to nexplinon and I waited like a month to get another thing in my arm I had one when I was about 5 months pp but haven't had another since I'm almost 9 months pp
Every body is different though I just had a similar experience
Every body is different, but I have the nexplanon and I randomly but rarely get my period.