It depends it could be pg usually ecm is a sign you are but some women experience dryness too. It could be a number of things. Have you taken a hpt? I would start there and then if still not sure have your blood drawn. Good luck.
I usually got really dry before my period and I don't remember having that feeling when I first learned I was pregnant. Considering you had your tubes tied, I think the chances you are pregnant are pretty low... You may want to take a pregnancy test, anyway.