Af 8 days late anyone have -s then a week later get ++?

So I had a MMC with my first in July before and after my cycles have ALWAYS been 29 days. Never I mean never have I been even a day late and here I am 8 days late... I took hpts a week ago all negative had a blood test on the 2nd nurse called said it was negative but if I implanted later than my first I wld of only been about 7-9 days so it would literally be impossible for hcg to show up over 1 which is what I was... my boobs hurt, hungry more, I always pee a lot so thats nothing new lol, wake up every night sweating so I haven't been sleeping much, lower back ache inc... my question is has anyone experienced this before? Gotten all negatives then a week or so gotten positives and went on to have a healthy baby? I feel like I'm losing my mind!