Implantion or period?

I have been spotting for the past 3 days. It’s light brown -dark brown at times. Not even enough for a pad- just a panty liner.

No other symptoms until tonight I began having lower abdominal cramping.

More likely implantion bleeding or a very light period. ? I am coming off depo- been without a period for 2 years- but just got put on nexplanon about 3 weeks ago. Sexually active since 5 days after the nexplanon was placed- no condom used.