i think it can b due to over stress of your body mostly...
1-2 hours daily in a gym?? you're gaining more muscles then...especially on the threadmill...muscles tend to b more heavy than fats..

don exercise immedietly after food even if its cycling bcoz if not mistaken that will increase your body's food uptake immedietly...so u absorb much more...

sleep earlier to let your body hv sufficient time to rest...
and always take breakfast!! especially if you're working so much on the weekends..bcoz if u don eat proper meals, your body goes into starvation mode where the metabolism and everything inside your body slows down and don work properly...so basically it lowers the rate where u burn fat even slower than normal rate...

all these info are from those articles i read from girl magazines health magazines online n based on hearsay oso la...

if your gym hv...ask the body trainer to help u train for lowering body weight rather than firming up...

oh was that her own baby??