Is it normal to deworm a cat and she lose her litter?

If she had a high worm burden she may have had a swollen stomach. This will have resolved once she was wormed properly. Wormers are very safe drugs & OTC are unlikely to have caused a problem.

Now she isn't feeding the worms she won't feel hungry all the time.

A cat with a high "payload" of worms will often have a swollen stomach, and it can look like pregnancy. She would have been eating large amounts of food to make up for what the worms were taking, and now that they are lessened (probably not gone) she doesn't have to eat as much. As soon as your vet is back in his office, get her spayed and take in a fecal sample - she probably needs to be wormed again. Most wormers won't harm a pregnant cat, but some of them can be toxic, so you do need to be careful. When you are in your vet's office, have him suggest a backup vet to you. You really do need one - you never know when you're going to have an emergency when your favored vet's on vacation!

Over the counter wormers could have killed those kittens IF she was pregnant. Never worm a pregnant cat. She needs to be spayed.