10 periods in 4 months!

Okay so: I’m on the pill- have been for over a year and it has all been fine and then September- December I’ve come on my period 10 times when it should have been 4 times. I normally take the pill for 21 days and then have 7 days off and that regulates my period but all of a sudden I would bleed through the pill even though I’m taking it as I have been for the past year?? Is it normal to bleed through the pill all of a sudden even though I’ve been fine with it for the past year?

I went to the doctors and come off the pill for the past month and it has all been fine, however I have to be on the pill otherwise I cannot handle my period pain so the pill was the only option, when I went to the doctors they changed my pill however as soon as I went back on a pill I’ve had my normal period and then a week later had another period? Even though I’m on the pill- I’m bleeding through it once again. Is this normal?? The doctor didn’t really say much about it except changing the pill. Help!!! Thank you xx