At the end of August I took Plan B as I had accidentally missed three pills (long story short my pharmacy messed up my pill brand and I accidentally took the inactive pills because they were the same color as my old active pills)

I have been consistently on my birth control pills since then, but the past two packets my withdrawal bleed has come on about three days before I start my sugar/placebo pills so I'm bleeding whilst still on the active pills.

Is this normal? I'm not having sex at the moment but I'm concerned my birth control pills are not working because I keep getting withdrawal bleed whilst I'm still taking active pills? I know the Pan B pills do throw your cycle off but for two months after whilst on birth control pills that are supposed to regulate the hormone levels?