Hello Jennifer and Welcome to Fish Lore

. It does indeed sound like your Platy is pregnant. Should she give birth inside the tank the fry could very well be eaten by other tank mates, this also includes the parents. You can purchase breeding boxes that float in your tank to house the expecting mom in. Sometimes this may cause a lot of stress for the mom though. You just never know. Personally I would leave mom in the tank or give her a tank of her home to birth. If you leave her in the main tank, make sure the babies have plenty of places to hide. This way you might have a few to survive.
Best of luck and keep us posted. We love photos around here as well

Have fun and enjoy the site. Best of luck!
Ken
