Period haven't showed and tested negative on stick

My period haven't showed up and I'm not spotting either. I have been having stomach pain and cramps for the past week and a half. I still have them and I haven't been eating much plus my nipples a lil sore but I think it's the cold because I use to have them pierced. I tested the first day when my period was supposed to show and it said negative. So what should I do now, I'm totally clueless???

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