2% Condom Failure?

Hi! This might seem like a stupid question but I can't find the answer any where.

My SO and I have used condoms everytime we had sex and none have broken (well one did but he noticed instantly and took it off, put on a new one).

The reason I'm asking about the 2% fail rate is, can you use a condom, not have a visible break, and get pregnant?

I am a week late on my period. I didnt think much of it because I have PCOS and late periods are nothing new. But, I started having a lower back ache, am way more tired than usual and this morning I threw up and all day I've had that like frog in my throat feeling.

I took a clear blue digital test yesterday and it said not pregnant but still no period. I bought a first response one that I am planning to take on Saturday if AF doesn't show.

Opinions?