Could I be pregnant?

Alright girls, According to my tracker My period was supposed to start the 19th and I am now 4 days late, yesterday I took a home pregnancy test and it was negative. My periods are usually irregular but usually only by a couple days. I have every sign of a period, sore boobs, face breaking out, cramps, bloating. Although they are also signs of pregnancy. But I have been stressing a lot lately with school and my fiance being over the road driving, and worrying about if I'm pregnant or not. I've also noticed this time that my lower back has been hurting for the past 3 days. Today it hurts from my right abdomen to my back and it hurts to walk and sit. But I do have one more test left I figured I would test again in a week if it does not start by then. But do you think there's a possibility I could be pregnant?