Have not missed any birth control pills and consistent with the time i take it each day how likely is it to become pregnant as the only contraceptive?

Unlikely: If taken properly and reliably birth control is a very effective means of reducing the chance of becoming pregnant (around a 1-3% failure rate). The common reasons for birth control 'failure' is being noncompliant with the medication or taking another medication that interferes with the birth control pill (some antibiotics for example reduce BC effectiveness).