Birth control question

Okay I’m a little over a month and a half into taking my birth control. No side effects other than some acne problems but nothing too crazy. Except for a couple days ago i started bleeding pretty heavily. The blood is a lot thinner than my normal period blood but there’s a good amount of it. I’m in the middle of a pill pack. I shouldn’t start my period for at least another week and a half.

Has this happened to anyone else?

Is this normal?