Hi, Starlynn!
Welcome to Rescreatu! We're glad to have you. :)
On your hatchery, it will say how many hatches you've used up, right above the egg and filter drop-down menus. For example, mine says: At this time you may only hatch up to 1 creatu each day. This means you have 1 hatches left.
If you still have one hatch left according to this, you should be able to hatch another pet. If there are 0 hatches left and you don't have 3 pets, you could possible have hatched one, not named it, and forgotten. If this is the case, there should be an alert at the top of the hatchery page under the blue navigation bar telling you that you have 1 Creatu awaiting a name.
Hope this helped! If you have any more questions, I'd be happy to help.