Shaykh Abdul-Hameed Al-Hajooree hafidahullaah was asked a question:
Is it legislated for me to say Ameen to my dua, (meaning) that I supplicate with a dua and after it I say Ameen?
To leave it off is (what is) appropriate. There is no proof for it (i.e. To say Ameen to your own dua). And if you were to say ameen (upon your own dua’) based upon the ameen that is said after (reciting) faatihah, then there is no harm in it”
Abu Mu’adh Mahdi