No. Ditto is a very special Pokémon. Ditto is also the only Pokémon that can breed with a legendary Pokémon or its offspring, as well as the only one who can breed with genderless Pokémon at all.

Can 2 dittos make an egg?

No. Ditto is a very special Pokémon. It can breed with most Pokémon, regardless of gender (or lack thereof), and the egg produced will always belong to its partner.

Can you breed a Ditto to get another Ditto?

Ditto: Both Genderless and the sole member of the Ditto egg group, this Pokémon can breed with any Pokémon that is not a member of the No Eggs group. It cannot breed with another Ditto, however.