I haven't read all the posts but I am sure everyone is giving their anecdotal stories that they couldn't get pregnant at 33 or did get pregnant at 43. I've seen both. Most people have no issues at 33. Some people have no issues in early 40s. But remember for all women fertility begins to fall after 35 quickly, so if you want 3, you are really pushing it to start at 33 even with great fertility. I recently saw this article (albeit in the daily news) that makes this point well. If you want 3 kids, it is a risk for any woman to wait till 33 (again, recognizing that there are lots of women that have no problems in late 30s/early 40s).
http://www.dailymail.co.uk/news/article-3104023/NHS-chief-warns-women-not-wait-30-baby-country-faces-fertility-timebomb.html
My own story is that I could not get pregnant when I tried at 30 without medical help. By 34 when I tried for second my fertility was nearly dead. Took 8 IVFs (which most people cannot afford and which emotionally was horrible) and I am finally pregnant with #2 at 37. I wanted 3 but I have accepted it probably won't happen. I would NEVER advise waiting, or at least, go get a fertility workup to see where you stand.