Re: Extended nursing and ovulation
Is it likely that your daughter's nursing is affecting your cycle? Maybe. I think "possible" would be a better word. She's 3.5 and no matter how often she's nursing, it's probably not that much compared to an infant or young toddler. In general, once a mom's cycle comes back and has been back for a while, it falls into a pattern that is similar to your pre-baby norm. If you were clockwork pre-baby, you're likely to still have regular cycles. If you were erratic per-baby, then you're likely to see erratic cycles.
There are other explanation for erratic cycles, and if you want to conceive again I think it makes sense to eliminate them. Charting may help. I would pick up a copy of Toni Weschler's book "Taking Charge of Your Fertility" and a good thermometer, and start charting your cycle, paying special attention to thermal shifts and duration of fertile-quality cervical mucus. Then check out the "Troubleshooting Your Cycle" section in the back of the book, and see if anything strikes you as wonky. Also, if you haven't had your thyroid tested since you gave birth to your first child, I would have done now; thyroid problems affect about 5% of women in the postpartum year and about 1% become permanently hypothyroid. And of course thyroid function affects fertility, and often shows up as an unusual cycle.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"