what if my hamster is not pooping

My dog suddenly woke up and started licking and had audible swallows and seemed distressed. I got her some water and she didn't drink... I also ran my hand over the outside of her throat and she gagged when I hit a certain part, but then she has stopped the licking and swallowing. Is this something I need to be worried about? She seems fine now.

I noticed my cats have fleas last week and applied Advantage 2 for large cats (over 9lbs). I squeezed the entire tube on to the skin between parted hair at the base of the skull. A week later, the fleas do not seem to have gotten any better. I'm concerned that my cats might be too large for the medication to be effective. They are 17 and 18 lbs and it's not just bc they are overweight. My vet said that while she has seen fatter cats before, the 18 lb cat is the largest cat she'd ever seen. Could their size be a factor in the medication not working? I've put Sentry flea collars on the cats today, washed all the linens in hot water, applied Sentry Natural Defense flea and tick powder to the carpet and upholstery and today I washed the one cat that will tolerate baths with Sentry Purrscriptions Plus flea and tick shampoo. What should be my next step? Can I reapply the advantage before the month is up? I've read that it is one of the safest and most effective treatments for cats. I tried calling their hotline, but it's only open on weekdays. These fleas are driving me crazy :-(