I went to the emergency room they said i have a cyst on my ovaries, the doctors said get on birth control why i do i need to get on the pills i'm fat?

Hopefully: They referred you to the gyn on call for the er they should ahve expalined why to you, but if you ahve a simple fluid filled cyst , the bcpills can often shrink the cyst , so u need to see a gyn asap so he can treat you and you have to make sure the cyst goes away and doesn't get larger or rupture, and many of the newer pills you shoudln't gain weight, I use low dose ones in my pts lessor nowtgain.