Has anyone ever took one of them early pregnancy test & it came up ''NEGATIVE'' but ''POSITIVE'' days later?

Ive tookin 2 pregnancy test one in the morning & one the same day in day both ''NEGATIVES'' & its heart braking when you only see just 1 line (GRRRR) i already a 2yr old child & have been trying for 2months now, i have an ovulation test kit called ''OvuPla'' & me & my partner had HEAPS when i was ovulating SO WHY ARENT I PREGNANT? i didnt get it, why is it coming up negative, I took them pregnancy test where you can test 5days BEFORE our missed period & i am due for my period THIS saturday the 21st, i ovulated a couple days later than i usually would ovulate but im thinking if its coming up negative maybe the baby hasnt implanted it self to the uterus wall yet? or theres not enough HCG in my body to detect pregnancy yet? i dont know! SO CONFUSED!!!!, Has anyone ever got negatives & then missed a period & THEN FINALLY got a positive result? When will i get a positive if i am? this is bull-**** & want another child so bad why can it just happen? Any different information PLEASE?