Does anyone have suggestions on how to conceive?

My fiancee and I are ready to settle down and start our family off, but the problem is, I can't get pregnant and I don't know why. I have gone to a doctor and asked to find out whether I am fertile or not, but the doctor thought I had appendicitis. So I never found out if I was fertile or not. This is worrying me so much as I really want to have kids in my lifetime. I know I need to change my diet and start to exercise more, but i am living with a friend who doesn't eat and therefore I have to go to my soon-to-be in-law's house to eat and it's stressing them as much as me. I am only 18, but I feel as if I am completely 150% ready for a child. So, please, can anyone help me?