Thanks for your query.
It is very common with the contraceptive
implant to have irregular and delayed cycles.
many women menstruate irregularly with that.
SO your delayed cycles might very well be due to the Implant only.
However, pregnancy is always a theoretical possibility with a missed period, albeit the chances are less at 44.
Please take a urine pregnancy test to be sure.
Better still, consult a gynecologist for a blood test
/ pelvic ultrasound
to confirm the pregnancy.
Make sure you always are on reliable birth control , till you attain menopause