When should I make an appointment?

So I have been tring to conceive for about six months now. There is no luck and I'm wondering if maybe I should see a dr and see what's going on, but I'm unsure if it's to soon and I'm just worring or if there could truly be a problem. I don't not know on average how long it takes women to conceive. Can some one help me and let me know if I'm just worrying and how long it took them to conceive?