Contraception worry

[Applescruffle]

I'm a bit worried about something and wondered if anyone had advice.
In June 2019 I had a contraceptive implant fitted. I was sure that at the time they told me it lasts for five years. As its now five years, I've just called to make an appointment for a new one and was informed that actually they only last for three years and I should have had a new one by now.
My question is, if I've effectively been without contraception for two years how the hell am I not pregnant?
I 100% never want to be pregnant again but I'm worried there's something wrong with me now. Could it be that the implant lasted longer than it's supposed to?
TIA

Yes. So they will "guarantee" it at a certain level of effectiveness for a period of time. After that the effectiveness will dwindle. So if it's still semi effective and you don't hit your most fertile days then you won't get pregnant. But not what you want to rely on!