If you are using birth control pills regularly chances of failure or that of pregnancy
is 0.5 %
with condoms there is 20% failure rate and hence 20% chances of pregnancy.
If your cycles are regular,then it is around the time of ovulation that you have maximum chances of pregnancy,in a 28 day cycle usually day 10- day 21 are considered fertile +/- 1 or 2 days .
there are chances of pregnancy with the clear liquid also if you are in your fertile period.