Help please

Iv posted this before but I don't understand what's going on and have fear of having another eptopic... I am 22 years old and had an eptopic 4 years ago....

AF didn't arrive when it was supposed  to but at 7 days late I started cramping and spotting. cramping lasted 2 hours then went away and spotting lasted 3 days and now it's gone. Last night I had horrible hot flashes that lasted 3 hours to where I was outside in a tank top still sweating like crazy and was extremely dizzy and faint .. My boobs have grown to where they don't even fit in my bra anymore. Nipples go from being dark to being a yellowish tint?? I feel so sick it's starting to affect my work today. Beyond tired because I couldn't sleep at all last night, had crazy vivid dreams when I did finally fall asleep and to top it all off this morning I have the headache from hell .. Tested this morning and It was negative so here's my questions for you lady's 

1) is it possible for implantation to happen after a missed period  (7 days late)

2) shouldn't I have a positive by now ? If I am prego or would I have to wait a few days (if this is implantation)

3) are hot flashes that last that long and are that extreme normal? 

Any help or advice or anything would be greatly appreciated cause doctors office is closed till Monday