I had injectable contraceptive and there was a reflux ...

I took the injectable contraceptive on 20/12 as usual (every day 20) and there was a significant reflux, my menstruation that was to come on the 10th came on the 1st. Is this proof that there really was a reflux of ALL the medicine? Should I take it again only on the 20th as before, or take now since the menstruation came earlier than expected?
Expert answer:

You should take it on the right date again and use a condom this month for safety.