If you are 57 the reason that you might now be having a period is that you have gone through menapause, if so then you are not ovulating anymore and I would guess your chances of getting pregnant are pretty low to none.
If you are still ovulating and had intercourse last Friday that would mean it has not even been a week yet, it is way to early to test and get anything accurate. It can sometimes take up to 7 days for the sperm and egg to fertilize. If you are pregnant you are going to have to wait a couple more weeks before a test is accurate.
um best i can tell u is go get a test and take it as soon as u get up(: and u cant get pregnant unless u have had periods