When to get help:)

Hello all, on the heels of being late 10 days and just starting AF I am here to ask when did you get help? I am 34 and hubby 36, we have a 4 year daughter and our son was born at 16 weeks in August 2013. Nothing since :( I feel like I am getting older, my periods have changed and I am getting worried it is never going to happen! When or what event did you it will you seek help at? Thank you kindly and good luck to all!