Unexpected breakthorough bleeding: freaking out

I’ve been on the same combo pill for over a year and haven’t experienced breakthrough bleeding since my first 4 packs. I’m also very good at taking my pill at the same time everyday. Suddenly, I’m breakthrough bleeding for 5 days (it’s still happening). I don’t know what to think or do about it. Could my last pack have been faulty? Any suggestions? Just kinda scared.