GD can show up as early as your pregnancy test....it is all very individual and has to do with the way pregnancy hormones make you resistant to insulin. It is picked up most commonly in the third trimester because this is when your body has peak insulin needs with bubs doing most of its growing then but can occur anytime during the pregnancy. If you are concerned just ask the doctor for a finger ***** test and that shoud give him/her some indication of whether you may need a GCT or GTT done...better to be safe than sorry....Having said that it is more than likely just the weather bothering you