I had a baby 19 months ago, and i am currently using Mirena IUD. I have really bad ovarian cysts, now n then..?

I have been having ovarian cysts that come and go. its been months since i have gone to the doctor about it bc they went away. but then they come back. i feel like im having pregnancy symptoms but bat the same time, i know its a cyst bc it feels the same as before when i had gone to the dr. They hurt so bad i cant even have sex with my fiance. and at the same times my breasts are really tender and feel like their bigger. i'm freaking out bc i thought that birth cntrol would help to make the cysts go away and i've had the miena iud before the cysts even came. So what the F is going on with me? it's confusing and annoying, and the dr told me the cysts should go away on their own. then why do they keep coming back :(