I have been trying to get pregnant for the past 6months. i have one child already. i have went to the doctor and thing was ok. ?

Time will tell: It's a bit early to start worrying about infertility after 6m. Some would not consider a full evaluation needed for you & your partner until 1-2yrs have passed. Try to simplify life & remove stressful pursuits that might put your system off a bit & followup with your doc if the problem persists.

Yes: It may take up to one year to get pregnant; after that, usually further testing is done. The good news is that you were able to get pregnant in the past. If everything checked out fine, you may just need a little more time.