Can BC lose it's effects after a long time of usage?

I've been on YAZ for about a year now. I started it because I have extreme PMDD and I was VERY irregular. For the first few months, my periods were very light. I had no cramping or bloating. Now my flow has become just like it was when I wasn't on the pill. My cramps are getting increasingly worse, but have not gotten as bad as they used to be. And now I get EXTREMELY bloated before I start and the first day.

So my question: Can BC lose it's effects after a long time of usage?

Thanks in advance!!

--LinZ