Was your period supposed to come on the 19th, or was it early? Was your period much lighter than your normal period? Sometimes women bleed a little and think they got their period when they were actually pregnant. Some women have bleeding throughout their pregnancy.
If you had sex five days before your period was due, it is unlikely that you got pregnant. However, it is always possible. Women's cycles can fluctuate and they aren't all the same.
Since your period was due around this time, you could try a pregnancy test now. Or you could wait a week for a more accurate result.
It is very common for women to be late by a few days here and there. There are a lot of things that can affect your cycle. Stress, change in diet, weight gain, dehydration, exercise, hormone fluctuations, etc.
Take a test now and in a week, if you haven't started yet. It should be accurate in a week as that would be the normal time to test.
Good luck!