Just 3 months ago, my period cramps would start on the day my period was due, but now I feel discomf…

Just 3 months ago, my period cramps would start on the day my period was due, but now I feel discomfort a week beforehand. Why has PMS started showing up earlier? I have such strong pulling sensations. I've tracked two cycles myself, had ultrasounds, and everything is great, my swabs are perfect too. But on the third cycle, the same pain?