trying to get pregnant

I have been trying to get pg for a year and a half now. I had the iud a few months took it out then was on pills about three months and nothing not for a year and a half..I have had two a ultrasounds done and this last one that was done showed my uterus was 18m idk what the meens if it is normal or not was just told to go see my women's doc.. Amyone have any tips? I di t know when I am ovolatingg cause my periods are weried. Sometime late sometimes eairly. I do t know how to cheke that temp thing. I a mom of four and I never have had this problem befor.. I was o e the shot with my first for years and never had problems getting pg..