I have the nexplanon birth control, so I know periods can be random and stop suddenly while on it. Anyway, I’ve had this birth control for about two years now, and so far, my periods have been pretty regular for the most part, lighter and last a shorter time, but usually are on time. Last month I was supposed to start my period on March 13th, but I didn’t. I did take a test, and it was negative. On the 22th-23rd I spotted about ten drops of old blood, nothing new, it was legit a few spots here and there, and that was it, so I didn’t count it as a period. Now I’m not sure if when I calculate when my period that is due this month (April) do I go by the 13th as missed, but I’d still start around that same time in April, or do I go by the few spots on the 22nd?
Take another test if negative I would make a doc appointment
I would definitely make an appt with your OBGYN. Have you always had irregular periods or just since you started BC?
The nexplanon causes very irregular periods and spotting. I used to work in OBGYN and more women got theirs removed than any other BC, more often than not, because of that. However, I do recommend another test if there is a possibility you are pregnant. Your doctors clinic could run a blood test to be sure. I’m kinda shocked if this is the first time this has happened since you’ve had it two years…but sometimes these implants have a mind of their own 
Mine were like this then just started getting it every 3 or 4 months it was lovely lol but maybe go to doc to have a test done
I get mine every 3 months, super light but it lasts two weeks with the nexplanon.
I quit bleeding on it 
it’s not uncommon for BC to change your cycle
The nexplanon causes irregular periods and spotting you could literally have a period every month on the dot then all of a sudden go months and months with just odd spotting. I wouldn’t worry about it unless you get any pregnancy symptoms.
Sometimes I go a full year without having my period.with nexplanon. This is my 4th year on it.