Late period...

My girlfriend is 3 days late on her period (last period happened on 15th of april - a day earlier then expected). She usually has a 28 day period... and it's been very regular so far. She didn't have any unusual stressful days so I'm really worried.

We only had sex 2 times - on the 16th of April and on the 29th of April. We use condoms and I always pull out so to minimize the risk. I'm 100% sure the condom didn't break...

I know we should take a test, but she is too afraid and I don't want to put pressure on her. What are the chances of her being pregnant?

PS: Her breasts seem somewhat smaller and stiffer and they hurt a bit!