Question about mat leave?!

Here in Ontario we need 600 hours to get maternity leave. I will be cutting it very close on whether I will get the full 600 before the baby comes. Depending on how many hours I can get each week and if the baby comes early at all. My question is if I don't get all the hours I need am I able to go back to work after the baby is born to get the hours and then apply for maternity leave?

If so will I'm assuming I can only be off for my 10 sick days allotted per year after she is born and then have to go back to get the hours?

I'm soooo stressed about all this :/