Just to make you aware, exercising is wonderful but when you first begin to do it your weight loss can slow or you might even gain a little. This is from water retention usually(and sometimes added muscle). Once your body gets used to it the weight will begin to come off again. Adding more water to your day can sometimes help as well.
You might consider putting away the scale for awhile and getting out the tape measure instead.
If you have noticed similar patterns like this in the wintertime in your life(loss of focus, decreased energy etc.) You might consider the possibility of having SAD(Seasonal Affective Disorder). Zuleika wrote an article concerning it. i think it is in the CAD/CALP section and there are many articles about it online. Here are a few you might find helpful:
http://www.outsidein.co.uk/sadinfo.htm
http://www.nmha.org/infoctr/factsheets/27.cfm
http://www.sada.org.uk/

Best of luck to You (all..smiles)