I Am Currently A Week Late On My Menstrual Cycle.

I am currently a week late on my menstrual cycle. I have never been late or missed a period. I have hip pain and lower back pain. No sore breast. I feel more tired but unsure if that's because my hormones might be messed up? I used to work out 4 times a week for 6 months and this month I really cut back due to working so much... I took a pregnancy test at lunch and it came back negative. Wondering if I could be pregnant and wondering what might be causing hip pain and lower back pain.