It depends on when you ovulate. Women who are regular ovulate about 2 weeks before the start of their cycle. If you have a shorter cycle, then of course this number goes down. If you are irregular, you could be ovulating at different times, so you would need to chart your cycle out, or get an ovulation predictor kit.

A period means that you are not pregnant the majority of the time. If you miss a period, you can take a test to see if the reason why you are missing your period is pregnancy. You can have a late, early, or missed period because of stress, so a missed period is not always a sign of pregnancy either.

i used to be regular , untill i stoped bc !
now i never no whats going on
but like i had sex bout 2 in a half weeks ago .. kinda starting to wonder if i am now.
Seems like .. im having tones of heartburt & feels like i can never have enough food , constipation
is all this way to early ?

It is possible, but 7-8 days is a pretty short luteal phase which is the time between when you ovulate and when you start your period. That is almost not enough time for the egg to fertilize and implant. Usually that whole process takes at least 10 days. That is for most people.

But with most things, anything is possible.