Is breakthrough bleeding on BC a sign of pregnancy?

I’m on birth control. I’ve been on for years and have been on this particular brand for more than 6 months. I take my pill at different times each day, but always the same day, my doctor said that was ok. I have Never had breakthrough bleeding. I start taking my inactive pills on Thursday. I usually start my period on Sundays. But for some reason, I have been spotting on my active pills since Monday!? Is that a sign of pregnancy? I know implantation is light pink and can occasionally be missed so I don’t think it’s that. But my best friend said that I should test because someone she knew had the same situation and she ended up pregnant.

Is that a sign or am I just breakthrough bleeding for no reason?