What's the earliest you can find out if you are pregnant or not?

You should miss your first period prior to taking any tests. It takes about this long for the pregnancy hormone called hCG to build up in your system.

Typically 4 weeks from your last period... The HCG will build rapidly during the early stages of pregnancy, causing a positive test result... 4 weeks

It really depends on what kind of methods you are using at home. If you are intensively trying to get pregnant, you may be tracking your BBT, in which 18 days post ovulation you will know if you are pregnant or not.

If you are simply going by HPT... then the earliest would be when you miss you period, the week of, or it could take a few weeks after before it registers on an HPT.