When I was going fertility treatments the doctor had me come in for a blood test on the day that my period was scheduled to start...two weeks after they did the insemination. Some of the home tests say that you can take it earlier, but I'd wait until at least the day your period is due if not one or two days after.
You can take a blood test about 14 days after unprotected sex. Some urine tests will pick up results as early as 21 days after unprotected sex, although the results will be much more accurate after 27 days.
some test say you can take it up to a week before your missed period but i think you should wait atleast until your period is a week late. so you get the most accurate reading. it doesnt matter if you get a dollar store brand hpt or the most exspensive htp they are all the same they measure the hcg in your urine so i would wait a week so you get the most accurate reading and with the blood test you can get one as soon as you want because they detect even the lowest level of hcg