Nurvous

I'm 21 years old, and my boyfriend of almost 4 yrs has a 4 year old son from a past relationship. When we first started dating my Boyfrined and I had unprotected sex and I had gotten an STD. Which I was treated for many times. Now I would love to start a family of my own. I"m pursuing a career in nursing, still in school of course. I just had my period the last week of November and I've been plannning my ovulation and when to have sex and what not. But deep down I am very afriad that it wont be easy for me to have children or even imposible. I would love to be a mom and I know i'm young and not married yet but I feel like if I don't start trying now I will never get pregnant. I have expressed my feelings to my boyfriend but like a typical man he says "everything will work it, don't worry about it." I just can't help have this feeling in the back of by brain of worry. I have been off my birth control since this summer but we have used the "pull out method" (if you want to call it a method.) and i assumed I would get pregnant because it is not an effective way to prevent pregnancy. But in the last month I've started to want a family and my boyfriend and I have decided to start trying. We are very excited and would love to have a girl. This is the first month I have planned when I ovulate, I also started to take prenatal vitamins and the first pregnancy test I can take is on the 21st. And im very scared to know if I am or not. It would completely devistate me if I could not get pregnant easily.