Thank you for your query.
A fundoplication would not cause nausea
after a month, specially when you were okay in the interim period.
However it is worthwhile to consult your surgeon, because that seems to be the most logical conclusion.
Otherwise, extreme nausea could be due to gastritis
, or early stage jaundice
, or some hormonal
medications you are taking.
As far as the pregnancy
is concerned, you would only know for sure when you take a pregnancy test.
THe earliest you could do that is a few days after your missed period, so it is too early for that.
I would recommend a consult with your surgeon, and evaluating gastrointestinal causes of the nausea.