Am I pregnant 3 weeks late period??

Hi I'm 20 years old and have had a normal period same day every month since I was 13 maybe 2 days max overdue.I am now 3 weeks late for my period. I had sex in June there bout a week after my period and then no period in July and doesn't look like I'm going to get one in august. I've has a lot of White discharge no smell itchy or pain, nausea and painful twinges in my uterus, and dhiarea but have taken 6 pregnancy tests and all negative no stress or contraception either. Thank you please help 3 weeks late now