Help. Why can't i seem to conceive.

Hey I'm a happy mom of two little girls both of which I got pregnant with completely just randomly wasn't trying wasn't ready definitely wasn't with a guy worth having a kid with. After my youngest I got on nexplanon and had it removed early this year. Now my cycle has regulated and has been regulated for the past like 4 months, I seem to be regularly ovulating cycling and what have you but no pregnancy. What can I do to of my chances food-wise exercise wise sex timing-wise