Like nothing is guaranteed of course but I'm pretty convinced that Sansa is more likely pregnant right now than she is not based on the following evidence.
The fact that 20-30% of pregnant people don't actually suffer nausea so Sansa having a steady stomach doesn't mean much. To add to that we have the example of Sansa remembering how Catelyn was never queasy while carrying Rickon but was hungry as hell.
Which brings me to the next point. Change in appetite. Sansa doesn't have a really big appetite to begin with (although baby girl is a sweet tooth) so the fact she's hungry all the time now... hmm.
Missed moonblood. Sure, it's not uncommon at all to miss a moonblood. But given that Sansa's cycle has always been fairly regular...
The fact that you write her having other common pregnancy symptoms like tender breasts.
These aren't "physical" based but still relevant. We know Catelyn concieved Robb within the first two weeks of her marriage to Ned (because that's how long Ned stayed at Riverrun before riding out to war) Sansa and Olyvar by Jaime last POV have been intimate for a lot longer than they were (although not much, given how long they were married before consummating) so I don't think them concieving quickly is too out there?
The irony of Cersei implying that Sansa must be barren because she's been married to Olyvar for 5 years with no kids when in reality they only consummated it recently and she is in fact pregnant right now
My guess is that if I'm right, it'll be confirmed in either Sansa or Arya's last POV for part 1.
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