Just a little fyi. If your periods are, in fact, 35-40 days long, then you most likely ovulate around day 21-26 or so. If you're still shooting for the "standard" day 10-14 "fertile phase" you're missing the mark.
You see, there are two phases in your period - the phase between day one of your period and ovulation will vary widely (for me it can get to be at least a month long!). The second phase between ovulation and your first period day is pretty much 14 days (very little fluctuation there). Your best bet is to take a typical cycle (if you're regular) and count backwards 14 days to get an idea of your ovulation time. Also it can't hurt to chart and take your temperature and or check your cervical mucus daily. Check out
taking charge of your fertility by toni werschler ( I never quite get her name spelling right). Arm yourself with knowledge. Four months is no big worry when it comes to not being able to conceive, really.
And like the previous person says - don't make it a chore - remember sex is fun!!