How long into a missed period will a pregnacy test work?

Hi I was wondering if anyone could shed some light on the matter, me and my husband have been ttc for a few months now, and I do know its a long bumpy road as have already got a 3 1/2 yr old girl, but this month things seem different, we have had sex every other day from 2days after the end of my period, but during the month my boobs seem bigger, tender nipples (nipples not so tender now), and bloated tummy (my tummy bloated like this before I found out we were expecting our little girl), the last couple of days I have had a little bit of whiwhitishscharge and yesterday it was brownish, but also I was ment to start my period yesterday, I done a HCG urine pregnancy test this morning but nothing, not even a faint line, how much longer should I wait to try the test again or is there another type of pregnancy test to do? I did have a appointment with doc this morning for blood test but when i got there they said she is off ill and earliest appointment is the 6th july. What do you all think and recomend?