My partner and I are trying to conceive. We started 2 months ago. My periods are always regular, and the first month we tried, my period came 10 days early, negative PT. After that period we were trying again, we have sex regularly 3-4 times per week, and did this unprotected all last month, however my period has arrived again, spot on to the new date from last month. How can I have 4 weeks unprotected sex and not be pregnant? I know its only been two months, but I m 25, regular with periods, and this is the first time I m having unprotected sex. My partner has already fathered a 2 year old from a previous relationship? Is my fertility in question, or is this normal?