Baby #3

So I've had 2 children already, 2 c-sections. Took me a year to get pregnant with my first, he is 9. Took me 3 months to get pregnant with my second, she is 5. Now I want another one, is this a pattern that I will get pregnant faster or do I actually have to calculate to get pregnant? I heard if you try it doesn't happen or it takes longer.... I'm 28 and I just wanted one more gremlin before I hit 30 :( I've only tried unprotected sex for a week though so who knows....