Can’t stop spotting after switching BC

I switched to a different brand of oral contraceptive about 9 months ago and I can’t stop spotting! Before I was super regular and ALWAYS got my period the day after starting the placebos. Now i never know when I’m going to start and I’m usually bleeding for 1/2 the month and spotting some too! I have been on BC for years and I have never experienced this. Why hasn’t my body adapted? - Also I take it a the same time of day and have never missed a pill