Four days late, yet tests are negative

I'm four days late and my period is extremely regular. 27 days exact every month. Me and my boyfriend of 1 and 1/2 years have unprotected sex with using the pull-out method and with no birth control. I took three pregnancy tests all came out negative. I'm freaking out because I'm never late. If anything I'm early! Everyone is telling me to wait to be a week late and then test again but honestly, I don't think I'm pregnant. I have no symptoms. The only thing that could be slightly related is that I'm pretty gassy lately when normally I'm not, and I'm sleepy all the time now. My nipples are a little tender but my breasts are perfectly fine. Am I over-thinking it? Or am I just one of those women that doesn't really have pregnancy symptoms? By the way, I'm 21 and I've read online a couple reasons, besides pregnancy, as to why I could be late. Yet those reasons don't really fit. Except I'm slightly over-weight. I have the same amount of stress each month and honestly I've weighed the same for a long time now. I worked out all week two weeks ago. This week though, I haven't done jack due to my tiredness. I'm honestly frustrated because I just want either my period to come or a pregnancy test to say I'm pregnant. I need an answer and I'm too impatient to wait. What should I do? Are my "symptoms" even remotely close to the "normal symptoms" a woman could have for pregnancy? Or is my body just changing? Please help.