Help!

I am currently on Cerelle (a type of birth control pill) I don’t get a period on this pill and I have been on it 9 months without any problems however I am sexually active with my boyfriend and we only rely on my pill, I have not missed a pill, taken it late or been poorly yet 1 week ago I randomly started bleeding as if it was a normal period but obviously I don’t get them anymore and this has never happened.. My fertile week was almost 3 weeks ago and I’m wondering what it could be? Can any one help?? Could I be pregnant and experiencing implantation bleeding?