How early can you take a pregnancy kit test for pregnancy?

I took my test 1 day after I missed my period as I was so sure I was pregnant. My morning sickness was so fast it began few days after conception. It is best to take the test 1-2 weeks after your missed period as the hormone levels should be sufficient enough to detect a pregnancy but it may or may not be accurate. I took my second test a week after my missed period and the line was so faint compared to my first test.