Period of implantation bleeding!?

Hey ladies, I’m supposed to be on my period right now and I am bleeding but in an abnormal way. I started my “period” a day early which is very unusual for me and it’s been extremely light compared to normal. It’s also been mostly brown/old blood. It’s almost more like spotting than a period. I also haven’t really been crampy which is also slightly not normal (I usually at least get some back pain/ discomfort). Does this still sound like it could be my period? I’m just nervous I’m pregnant. Also if I should test for pregnancy when can I do that? Should I wait until I stop bleeding or can I just do it now? My period was supposed to start today.

Also I am on birth control but I accidentally missed one pill this month (but we didn’t have sex that day or the day after).