The best way to get pregnant for larger women?

i have had regular periods for the last four years, and my husband and i are ttc we have had no luck, sometimes i stress and it causes a missed period, how do i tell when im ovulating, infact what exactly is ovulation, what is the meaning? i haven't been told that i couldn't get pregnant, i am pretty much new to this whole thing. someone said i should try to cut out cheese and such? im willing to try pretty much anything. im starting a regular workout regimen tomorrow. i have a lot of and so far nothing, what is the bbt? an how does it help you know when to try? i would do it if someone could give me a detailed description of how i do it and how it works. what position could better my chances, just anything you can input to my situation would be a great help...ok the day my period ends, where do i go from there?