TTC HELP!

Hi everyone! :) my fiancé and I have been TTC for about 3 years now. We have unprotected sex about 3+ times a week. My periods are kinda irregular. Sometimes they skip a month, randomly. Has anyone had success using this app? Should I go to a doctor? I went to my gynecologist and she was very rude & told me I'm too young to be asking questions like this. & I'm 18...my finance is 19. We both have full time jobs, our own apartment, ect. So if anyone has anything that will help it'll be appreciated! :)