I'm so sorry to hear about your struggles to have a baby. I've had a history with that as well and know it can be heart breaking to deal with so my heart goes out to you. My doctor had told me that losing even 10-15 pounds can increase your chances of pregnancy although I don't share your diagnosis. I did find this little fact though...."If you have PCOS and are overweight, weight loss may be all the treatment you need. Even a small weight loss can trigger ovulation. Weight loss of as little as 5% to 7% over 6 months can lower your insulin and androgen levels. This restores ovulation and fertility in more than 75% of women with PCOS" this was from Polycystic Ovary Syndrome (PCOS)-Treatment Overview
That is so great that you quit smoking today because WHEN you get pregnant, the doctor will tell you to quit anyway. If exercise is hard, I would just start in small steps. If 5 minutes of walking is all you can do, then that is better than nothing and you can work up from there. Good luck and please don't give up! The first step is to take care of you, trust me on that!