Weight loss

Been ttc for 15 months I have always been about 220 after stopping birth control I have gained 20lbs my dr keeps telling me to join weight watchers. I have hypothyroidism and pcos I exercise 3days a week and watch what I eat. Not convinced my weight is the sole reason for not conceiving nor do I thing my weight gain is from being lazy or over eating. Any is ideas of how to lose weight in my situation nothing I do is working what has worked for you?