Pill and different symptoms that normal

I have been on low ogestral for over 8 months. I have noticed mid cycle break throughs but just recently I have had heavy periods than I normally get with the pill. Just this past cycle, I got a heavy period like I was not a pill, then after my period my breasts have been very tender. Now, I have some brown spotting the week before my scheduled period week on my pill. The brown spotting has happened the week before my scheduled period last month too. Could the pill not be right for me anymore? Or could it be something else? I am 36 years old.

Thanks.