Efficiency of birth control Pill

[StarDreamer1184]

Hi I'm new here and Have a few questions regarding my birth control pills.
I have been on oral birth control for almost 1 year now (started for menstrual regulation) I am 19 years old and have just recently started having sex with my boyfriend. I know that if used correctly my pills have an almost 99% effectiveness against preventing pregnancy and we always use condoms also but I have been curious about just a couple things:
1) I take the pill at the same time every day as directed..but how much of a leinancy do I have before it starts to affect the effectiveness? I.E. If i take the pill every day at 9:00pm (+ or - a few minutes) but one day forget a little bit or get distracted and take it at 9:30pm is that going to make that much of a difference? I'm guessing it wouldn't since I can miss a pill in a week and as long as i take it sometime in the next 24hours my instructions say I wouldn't have to use another back up form. How does taking it at the same time increse it's efficiency?
2) I read somewhere that some multivitamins can decrease the effectivness..but can't find it now, is this true and how much does it affect it?
3) This one doesn't really have to do with birth control pills..but condoms...for sex in the shower or water do regular condoms work? I know the lubrication gets washed off and searching the site it said to use a silicone based lube..if we don't, aside from being painful, how effective would a condom be?
Thank you much

sam

[Cornelius111]

1. No taking it within an hour or two isn't a big deal provided you don't do it all the time. You should try and take it as close to the same time every day as possible, but if you slip by half an hour to an hour occasionally it's definitely not cause for alarm.
2. I have heard of St. John's wart affecting birth control but I don't know much about this.
3. Provided the condom stays on, which it should as normally, your only concern should be it ripping from lack of lubrication.