How do you know?

How do you know if it’s spotting, implantation or and actual period. I currently have the nexplanon implant so I know spotting is common. But it’s never been this frequent. Currently I am noticing some bleeding again this month and it is more of a brown color than normal. It’s not enough to really need a tampon constantly but it definitely has ruined the underwear I am wearing today. This has been my period schedule this month. Is this probably just spotting and possibly another period due to my birth control? My boyfriend and I always use condoms also and he pulls out before finishing so I know pregnancy is probably pretty unlikely