Me and my boyfriend have had sex 39 times and I still haven't got pregnant.

Conception is often a crap shoot. There are many factors that can affect it. Over what period were these 39 times?

As an aside, why not get married before you start trying for pregnancy?

Is that all? You do realize that it can take as long as a year or more of actively trying to become pregnant?

Is it right to assume that you want to be a single mother?

We have had sex 39 times in the past 2 months and we are engaged and will be getting married next year.

Then get married, get to know each other as husband and wife THEN try for a baby. Marriage is hard work. Many marriages don't work. When you add a baby into the mix before marriage you are increasing the chance of divorce.