Implantation bleeding or hormonal imbalance?!

Lily

So I’ve been on birth control for 2 years. I’ve never had spotting except for the 2 days before my withdrawal bleed. Last month I had brown spotting about 2 weeks before my withdrawal bleed. Now this month I’m having light pink/ brown discharge 1 week from my withdrawal bleed. I haven’t had sex, but my boyfriend and I have done sexual foreplay like things. If this is just hormonal imbalance, does this mean my pill isn’t working?