I have 5 kids and still have trouble saying I'm done. I love being a mom and it's all I ever wanted to be. I've always said I'm having 6 kids but I feel so overwhelmed sometimes with the 5 I have. My friend has 5 kids all the same ages as mine and knew she was done with number 5. I've never got that feeling that I'm done but at the same time I'm not sure if I can handle more. I think it is a really individual decision. We've had times where we have prayed and felt we should have more kids and other times where I just got pregnant. My youngest just turned 2 and I just turned 35 so times ticking...I still don't know if I'm done or not.
Good luck, I'm sure someone on this thread has better advice than me.