Is it time to start getting to the doctor for help with fertility?

Got my periods again this month after using ovulation test last mth I was sure we would conceive because I know when I was ovulating but we did not again, Im so disappointed. We are trying for 13 months and we have a child together already so know we can have them but its just not happening this time. I keep thinking this is the month yippee and then feel like I have pregnancy symptoms, then periods come. I think ill give up at this stage, what do ye think??