He didn't tell her. He lied to her. Again.

He didn't fall in love with a future version of her. He fell in love with
another Lois (a different woman) and couldn't have her because she was married. And the woman who should be
his Lois is dead. And the man who should be Lois's Clark is dead, too. And he took his identity.
That would be the truth.

If Lois thinks she's second best to her future self, imagine it if she knew it was
another woman...
Andreia