HELP!!!!

I'm 4 days late for AF, but when I have tested it always comes back negative. I have some cramping/tugging or pulling in the low middle of my stomach pretty much all the time and I'm nauseous. I just don't know what to think I've never had any of these kinds of symptoms. AF was pretty irregular due to PCOS, however the last few months have been regular until now. I think they were regulated because I started losing weight, which I still am. I've lost 29 lbs in 2 months. I'm not sure what is going on with AF. Curious if anyone has been late and gotten a BFP later than usual or if I should just expect AF to show up. I've never be pregnant and have no idea what to look for or how this all works tbh, it's all a bit confusing. Please help!