TTC and breastfeeding

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Anyone experience sensitive nipples during breastfeeding as a sign of pregnancy?

Noticed the past two days my nipples have been sensitive when my youngest feeds. I'm 4 days late but have negative tests so I'm wondering if maybe I didn't have enough of the hormone to catch on a test, but that maybe it is starting to build up more now as I would be(based of LMP) 4 weeks 4 days.