Any advice?

I'm currentl 15dpo, AF expected last week. Still not here. Usually with my period I cramp the the day before AF arrives. Then I cramp pretty terribly for the next couple of days and have such awful back pains that I usually end up throwing up. I started getting cramps last week and even went and got tampons because I was thinking "Oh, looks like I'll be starting tomorrow". Nothing. Haven't felt any other symptoms otherwise except noticing my boobs feel heavier and then yesterday I got hit with nausea at about 3pm that lasted pretty much all afternoon and all night. After I finally got some sleep I woke up drenched in sweat. Somewhat nauseous this morning. Stomach feels like there's pressure pulling in it sometimes where my uterus is. Took a pregnancy test on 06/07 and got a BFN. Decided to take one yesterday and then got a faint positive, followed by a few BFNs. Im so frustrated because I just want to know if I'm about to have the weirdest and craziest period of you life or if I finally have my little sunshine.