When I feed my kittens, I try to position them as closely to the same position they would be if they were nursing from their mama. Just be sure not to feed them on their back. Its best if they are laying flat with their heads up.

The average weight at birth is 100 grams and then they gain about 50-100 grams per week. They seem to be at good weights considering they look around 10-12 days old by sight. There will be small fluctuations in weight. Just be sure the weight loss isn't constant and that it goes back up soon.

I ALWAYS worry about the constipation too, but it always happens. Their little tummies get soooooo big. You can massage the tummy to try to loosen things up in there and then rub the bottom to see if anything comes out - that helps sometimes.