Bad cramping on the pill? Normal?

So I've been on the pill for 4 months now, after taking a year long break off it. My cycles were pretty regular and long without the pill, but I had severe and sometimes debilitating cramping that my gyno said it might be endometriosis so he put me back on the pill to see if it would help with the pain. 
Is it normal to still have bad cramps while on bc? Mine are still pretty bad but I thought that you weren't supossed to ovulate while on the pill? Is that true? 
Any advice?