Stress or possibly pregnant

How do I relieve stress? My period is 4 days late, but I took a test when I was 2 days late and it was negative. I just feel like crap. My whole body hurts along with my head. I wake up in the morning for work and I just feel sick to my stomach and dizzy. When I rest my body on my days off from work I start to feel better then I go back to work to 10hrs a day and it starts all over again. So I guess since I’m not pregnant how to I just relax and not stress. I’m just assuming since the test was negative that work has taken a toll on my body. I mean unless it’s possible that I could still be pregnant and my htc levels werent high enough to read the test