I'm curious as to what medication you are on for your PCOS. I was diagnosed with it 8 years ago, and was told then, and have been told ever since, that the only way to control it is with birth control. I have been on B/C ever since, but I went off of it to conceive my daughter who is now 5. I was very lucky and I conceived on the first try, before I even got my next period!
I have a 10 yr old, a 9 yr old, and a 5 yr old. They are all in school full time now, and I too have been thinking about having another one. I talked to my sister-in-law about it and she brought up some points that have really been making me think. She has 6 kids, ranging in age from 14 to 1. She says that one thing they struggle with is that there is almost nothing that they can do as a family anymore. Because of the difference in ages, there is almost nothing that interests all of them. What the 14 year old wants to go do, the 6 and 7 year old aren't interested in, let alone the 3 yr old and the 1 yr old! And then the 9 year old has his own set of interests too! Even something like Adventure Land is a hassle because of the age gap in the kids. She also pointed out that the physical demands of taking care of a newborn, that weren't so bad when she was 25, were a lot harder at 30! One thing that I had been thinking of myself is the fact that I now have 3 kids who are pretty self-sufficient; they can dress them selves, get their own food and drink, and other basic things like that. I have asked myself often if I want to go back to having a baby that is totally reliant on me for EVERYTHING! Another point that my sister-in-law brought up, that I have thought of myself, is that a newborn requires so much time. Because my kids (and yours) are now in school, we have less time with them. If I have another baby now, that takes even more time away from the kids that I already have. I will be constantly interrupted while trying to help them with their homework, or read to them, or anything else like that, that has become so much more important to me now that they are in school all day.
Anyway, I haven't made up my mind about having another baby yet either. I love being pregnant, and I love babies, and my soon-to-be-husband is pushing me because he wants US to have one together. However, I've been giving a lot of thought to the points I made above and trying to balance those points with my basic maternal desire to have another baby, now that my "baby" is grown and off to school. I don't know if these points will help you in your decision, but I thought it might give you something to consider as you work on making up your mind. Good luck, not matter what you decide.