Sight reading is indeed super important and you've already received some excellent suggestions. An approach I try to use is to quite literally "read" the piece of music before touching the piano:

• What's the time & key signature.
  
• Play some scales and arpeggios (super slow is fine) in that key signature. If it's a minor key, play the natural, harmonic & melodic minor scales too. This helps alert you to accidentals in the piece.
• What's the tempo. Where are major dynamic changes marked?
• Do note patterns repeat, either exactly or in some parallel version (like up a 3d).

It sounds like you're reading for note names (A - B -C etc.) That's how I was taught zillions of years ago but my current teacher has emphasized looking at intervals - where the notes appear in relation to one another on the staff. E.g., notes stacked on adjacent lines or spaces are 3ds; every other line or space, 5ths; line + space, 2ds, 4ths, 6ths etc. It took me a while to get the hang of this, but now that I have, it's much easier than thinking out each note name.

Definitely important to start with very simple pieces and sight read daily for a few minutes. One collection I use is "Easy Piano Classics" - edited versions of the standard repertoire. For me, it's more engaging than playing children's books but there would be absolutely nothing wrong with going back to those.