Are these symptoms of early pregnancy?

I am taking birth control but i did miss a pill by nine hours 3 weeks ago... I am having odd symptoms that have been evident for the last week. These are: sore breasts and nipples... almost tingly or something, slight cramps like I'm getting ready to start my period, dull back aches here and there, headaches, to much information but a slight white discharge, and the most recently crazy mood swings... one minute I'm happy the next I'm mad or crying for no reason. My period is now 6 days away. I have taken three tests now.... one when it was 8 days away, the next 7 days away, and then today 6 days away. All said negative. I just don't know if they were accurate though because the box says they are only 50% accurate 4 days away. I really just want to know for sure whats going on and why I am having these symptoms. I'm really worried.