Wants to know how long I need to wait in order for a positive to show...?

If pregnant, it happened around Marcth 30 or 31st. I was due for my period April 9, I missed it, still no sign... Took 3 pregnancy tests (dollar store brand) all negative. Really anxious.. ready for baby #2, my son will be 5 in June. I never miss my periods unless I'm pregnant, my period comes like clockwork... My sense of smell is stronger, im urinating more often, and I sleep all day... Somebody help me... Wat is going on? Is it that i'm just too early PERIOD.. since it would've just happened at the end of March or what? And howw far do you need to be for it to showw positive on a blood test????????? Really anxious