Friend might be pregnant

So I have a friend who is 17 and this month on the 5th she lost her virginity. She had sex again the nest day she says she used protection but shes starting to get worried she's pregnant. Her period is very irregular she says sometimes she can go two months without having one. She's worrying herself sick. To the point she feels like she's gonna throw up.

I need help exposing to her that it was only 19 days ago. Way too soo for the sperm to even take to an egg. Can anyone help?