When you use the pill correctly and consistently, it protects you well from pregnancy and your pregnancy risk during condom-less sex would be low. - However, your STD risk would be high, - as always when you are not practising Safer Sex and you and your partner haven't had at least 2 clean screens, six months apart.
Taking the pill "correctly and consistently" however, means taking the pill at the same time every day.
Whether being 11 hours late influenced your pill's reliability depends on your pill type and in what week of your pill pack: check what the insert of your pill pack says about missing pills or call your doc.
As you probably know, withdrawal is not a method of birth control (there is sperm in pre-ejaculate) - you hence had unprotected during a time when you might not have been fully protected by your pill, - and that's why you might want to think about emergency contraception.
I'd give the doc who perscribed me the pill a call and ask for her/his opinion. Also make an appointment for an STD screen if you and your partner haven't had two clean ones 6 months apart.
For more, check out
Planned Parenthood: Staying on Schedule Matters
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