Help??

Hey girls so I have a question so if someone could help me out that would be great. Okay so I’ve been on the pill for about a year now and recently I have started bleeding randomly, even on the hormone pill I will just start. I tired looking more into and I don know if it’s breakthrough bleeding (I don’t really understand what it means) or anything. I have been taking my pill at the same time everyday I never take them late. The brand is called Alesse. I’m slowly started to get more freaked out about it so if someone could help me out with this, it would really mean a lot :)