Can sinus problems be a sign of pregnancy?

No. Sinus problems are not a symptom of pregnancy. A positive pregnancy test is the most reliable way to confirm you are pregnant. Check one today.
Stuffy nose . Can be. See your ob-gyn to start folate (folic acid) if you're not on it already, even if you're not pregnant this time & avoid alcohol, tobacco or drugs including over-the-counter medications till you find out. Enjoy the adventure, if you are!