It could be! I know it was for me! My first pregnancy early I developed horrible horrible pain in my lower back, which can be mistaken for sciatica, but I'm pretty sure it was my SI Joint. With my second, one week after conception (pre pregnancy test) I started feeling my back in that spot. I told my husband I was pregnant, and he didn't believe me, but sure enough! LOL BTW- icing my back helped.
I had the same symptoms and took several pregnancy tests they all came back negtive. I went to my doctors and they did a urine test that came back negative. After that they did a blood test and it came back positive and I had a miscarriage at 7 weeks. So yes it is possible you are pregnant.
Its honestly a 50/50 shot, but when my period was late I was having the worse pain ever in my lower back because my body was preparing my uterus for the period. I say if you do not start in about a week take another test.
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