If you use your birth control correctly you will not get pregnant. The only way birth control can fail by itself is because of an incredibly rare genetic mutation you are born with, you cannot develop this mutation later in life, and you’d find out pretty quickly if you had it.
If you’re on a combined pill then you have a large chance you can miss a singular pill anywhere in your pack and remain protected. Most people don’t realise they have a 24 hour window, as there is only a select few combined pills that still work with a 12 hour one. Having a 24 hour window means you need to take at least every 48 hours to remain protected, as a 24 hour window starts ticking from the time you are supposed to take your pill. Always refer back to your pamphlet to get the instructions for your pill. It has this information.
As for bleeding and pregnancy: the bleeding you experience while using birth control is synthetic. It’s not real. It’s not a period as you do not ovulate. It’s either a withdrawal bleed (inactive days/break week) or breakthrough bleeding (active pills). While a heavy bleed is a decent indication you won’t be pregnant it does not guarantee you anything. There is also the option you won’t bleed at all using birth control, and that’s normal too. All and all only a pregnancy test can tell you. These are most accurate 21 days after unprotected sex. But if you use your pills correctly, account for interactions and follow your instructions you will not need to take any tests.
If you’re ever unsure about your protection status, always use condoms or abstain from sex. Plan B is much less effective than those options.
