I've been trying to have a child and i think o can't get pregnant why is that?

Many possibilities..: If you and your partner having been trying to conceive for over a year without success, then an evaluation started by your GYN and likely referral to an infertility specialist is in order. There are too many possible reasons to start guessing as to why you haven't been able to conceive. Be seen (along with your partner!) to start the process.

6 months: You have to be trying for 6 months with your partner and using scientific methods. If you then do not become pregnant time to visit the fertility specialist