If you value your breastfeeding, please, reconsider your decision to start _any_ diet when your baby is this young.
I'm very sorry if this sounds harsh but I am both a long time weightwatcher and a breastfeeding support mother.
Here in Finland WW says that a nursing mother may start their programme when the baby is at least 4 months old and is not exclusively breastfed anymore. You say your baby is 5 weeks and you've noticed a decline in your milk. This is a clear sign saying that continuing with the programme could seriously compromise your supply. The milk supply is very volatile for the first 8 weeks, some experts say that the first 12 weeks are crucial.
You can find more information about losing weight and breastfeeding from the La Leche League's webpages
www.lalecheleague.org
Enjoy your new beautiful baby and let the weight loss wait for a while. Babies grow faster than we can imagine and soon there will be a perfect time for you to start a weight loss programme.
best wishes,
anna, mom to two beautiful girls, a breastfeeding support group leader and a long time weight watcher