How likely is it for me to get pregnant with precum if i didn't take my birth control for a week straight... & missed pills throughout the month?

More than if didn't: Precum contains sperm; all you need is one to get pregnant. That's why withdrawal method doesn't work. Besides, we're clueless so don't trust us to withdraw in time. Instead, trust birth control pill/shot (but only if used regularly) & condoms (each & every time!). More likely to get pregnant if you don't take pills as directed. Skipping pills increases risk. Consider pills+condoms 2 prevent stds.