The last day of my period was sept. 11/12. I had sex on the sept. 13th but my boyfriend never ejaculated. I would say around the 22 my breast became slightly sore on and off but my nipples are continuously sore.I took a pregnancy test (a cheap pregnancy test), it read positive. I went to see my doctor and she told me my pregnancy test was negative but I had BV. My period is due around the 5/6th of oct. and I took another pregnancy test and it was negative... but my nipples are still sore.what does this mean? Is it normal to have sore nipples nearly 10 days before your period or is it just to early to tell if I'm pregnant ? Also I am a smoker but lately when I do, I feel slightly lightheaded, so I stopped completely

Yes doctor is right you would not be pregnant since you had sex just after your periods so your don't have any mature egg to be fertilized, so just cool down there is nothing to worry.
Regarding the soreness in your breast yeah sometimes it is possible to have it even after your period. It is generally because of high progesterone level in your blood, or sometimes its due to your diet ( like high on salty, high caffeine intake).
Don't worry its just normal :D

Menstrual and pregnancy symptoms are just too similar to draw any conclusions.
There are going to be unusual months at times, with hormone fluctuations, and only a test will be accurate.