D.B.
"Only 3 weeks off" is enough to throw your cycles out of whack. Remember that a "period" on birth control pills is not a real period - it's controlled by the absence of hormones during that week off. You started back up in September and say your period "continued to be regular" but, really, you only had one, right? So that's not enough to go on.
If you go off BC pills, you use another method of contraception until you've taken enough to be safe. And breakthrough bleeding is very common on low dose pills - not harmful, but it doesn't mean it's a period.
Use panty liners, keep a record of all of this, and use a condom until you are sure you are protected. Call your doctor or whatever healthcare provider gave you your prescription if this doesn't level off in a few weeks. Have that log sheet ready in case they ask questions.