Nexplanon birth control

I have the arm implant and have had it for about 4 months now. When I first got it, I didn’t have a period for 2 months and then it lasted 12 days. Now I just started my period yesterday and it was late by almost 3 weeks. Is that okay while I’m on the nexplanon or could that mean that it doesn’t work. I thought either you spotted the whole time you were on it or it took your period away completely. I just kinda want to know what other women’s cycles are like on it. I can still feel my implant and it hasn’t moved much, so it should be working, but I’m paranoid