First time on the pill

So I am just starting my second period on the pill. Last months period was HELL, by far the worst I have ever had, it was insanely heavy and I was changing my cup almost every 1-2 hours instead of it lasting me all day then again all night. I was told by my doctor to start taking birth control because my periods were super irregular (like over a year in between). Is this normal for being on birth control and will it really last like this for 3 months like some people say, or is this not normal?